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A young star, in the throes of the formation of its solar system, will be surrounded by a swirling disc of gas and dust capable of spewing out a powerful, jet-like whirlwind, something scientists had never been able to observe — until now. Researchers observed the jets around a protostar about 450 light-years away using the Atacama Large Millimeter Array (ALMA), which seems to be on something of a tear lately, discovery-wise. The winds lift stellar materials up from the disc as it forms the new solar system, kind of like a tornado lifting objects from the ground. The findings were published Thursday in the journal Nature.
We care about these whirlwinds because learning about them changes our assumptions about the process of planet formation. We used to think they originated from inside the protoplanetary disc’s center, but being able to study them in detail for the first time has actually shown that might not be the case.
“During the contraction of the gas cloud, the material begins to rotate faster and faster just like a figure skater doing a pirouette spins faster by pulling their arms close to their body. In order slow down the rotation, the energy must be carried away,” said Per Bjerkeli, a postdoc in Astrophysics and Planetary Science at the Niels Bohr Institute at the University of Copenhagen and Chalmers University of Technology in Sweden, in a news release. “This happens when the new star emits wind. The wind is formed in the disc around the protostar and thus rotates together with it. When this rotating wind moves away from the protostar, it thus takes part of the rotational energy with it and the dust and gas close to the star can continue to contract.”
The researchers don’t yet know what happens to the material that gets blown away — whether it eventually falls back to its origins or gets carried away into space. While the recent analysis doesn’t get into this explicitly, this is an important area of study because it potentially impacts how life is formed on other planets. If the material is indeed expelled into space for good and ends up one day seeding microbial life elsewhere, it’s important to know that that life has its origins in faraway extant space. This is why when we search for signs of life in our own solar system, we take separate approaches to, say, Mars — where any life, should it exist, could have originated on Earth or vice versa — and to distant ocean worlds like Titan, where any life we find is sure to have developed through an entirely separate process than life on Earth. | 0.823968 | 3.96488 |
There is a popular image of the atom that shows the nucleus as a collection of balls, with ball-like electrons following circular orbits around them. The parallels to our own solar system, to the orbits of the moon around the earth and the earth around the sun, strike a chord with most people, but the depiction is inaccurate. It is based on the ideas of several prominent early twentieth century physicists, developed after the discovery of the electron in 1897 showed that atoms were not the smallest building block of nature. There are two serious mistakes in this image, and the actual structure of the atom is a lot more interesting.
The first problem is that the proton itself is not an indivisible particle: it’s composed of three quarks, subatomic particles which were hypothesized in the early sixties and observed in experiments beginning in the late sixties. The same is true of the neutron: it’s also composed of three quarks, though the flavor composition is different than that of the proton. (“Flavor composition”? Yes, quarks come in different flavors.) So those giant balls in the nucleus are actually comprised of smaller particles. At this point we believe quarks to be themselves indivisible, not composed of another even smaller particle.
But the second reason this picture is incorrect is that the electron doesn’t follow a linear orbit around the proton, the way gravitationally orbiting bodies do. In fact, due to the small mass of the nucleus and the even smaller mass of the electron, gravity is the least important force in an atom. The electromagnetic force, between the oppositely charged proton and electron, is much larger than the gravitational force between these tiny objects. But wait, you might say, if there’s such a large attractive force, shouldn’t the electron just spiral into the proton? This quandary illustrates perfectly why we can’t rely on classical physics, which was built up for objects comprised of billions of atoms, for the particles within a single atom. Because yes, if we had two oppositely charged billiard balls that have a weak gravitational interaction and a strong electromagnetic interaction, they will crash into each other! But, the electron is so small and so light that we cannot treat it as a classical object.
Here is where quantum mechanics come into play. Quantum mechanics as a whole is a set of mathematical constructions used to describe quantum objects, and it’s quite different than what’s used for classical, large-scale physics. There are all sorts of interesting consequences of quantum mechanics, such as the Heisenberg Uncertainty Principle, which states that for some pairs of variables, such as energy and time or position and momentum (mass times velocity), how precisely you can measure one depends on how precisely you are measuring the other. For each variable pair, there is a basic uncertainty in the measurement of both, which is very small but becomes relevant at the quantum scale. This shared minimum uncertainty between related variables is a fundamental property of nature. For momentum and position, this leads to that old joke about Heisenberg being pulled over for speeding: the police officer asks, “Do you know how fast you were going?” and Heisenberg responds, “No, but I know exactly where I am!”
What the uncertainty principle means here is that the electron is actually incapable of staying in the nucleus. Imagine a moment in time where the electron is within the nucleus: now its position is very well known, so there is a large uncertainty in its momentum. Thus the velocity may be quite high, which means that a moment later the electron will have moved far from the nucleus. In fact, because of the uncertainty in position, we cannot ever really say where in space the electron is. It is more accurate to talk about its position as determined by a probability cloud, which is denser in places that the electron is more likely to be (near the nucleus) and less dense where it is less likely to be (far from the nucleus). This also takes into account the wave nature of the electron as a quantum object, which we’ll get into another time.
With this knowledge, we can discard that old image of an electron orbiting a nucleus. A single electron, even though it is measurable as an individual, indivisible particle, exists as a cloud around the nucleus. The shape of the cloud is described by quantum mechanics, and as we add more electrons to the atom, we will find a whole gallery of electron cloud shapes. These shapes are the heart of interatomic bonding, as we will see. | 0.837675 | 3.995964 |
NASA has attached its next spacecraft bound to explore Jupiter to the rocket that will launch the unmanned probe towards the gas giant next week.
Technicians wheeled NASA's Juno probe to its launch pad at Florida's Cape Canaveral Air Force Station this morning (July 27), then mated the craft to its Atlas 5 launch vehicle.
The event marked a key milestone for the $1.1 billion Juno mission, which aims to shed light on the origin and evolution of the solar system's largest planet. The rocket will launch Juno probe toward Jupiter on Friday, Aug. 5, mission scientists said.
"We're about to start our journey to Jupiter to unlock the secrets of the early solar system," said Juno principal investigator Scott Bolton, of the Southwest Research Institute in San Antonio, in a statement.
"After eight years of development, the spacecraft is ready for its important mission." [Photos: Jupiter, the Solar System's Largest Planet]
Closest-ever look at Jupiter
Juno will get closer to Jupiter than any other spacecraft in history — but not for a while. After its launch, the probe will cruise through the solar system for five years, finally arriving at the gas giant in July 2016.
Once there, Juno will undertake a year-long science campaign, studying Jupiter's structure, composition and magnetosphere, among other things, researchers said. The overall aim is to get a better idea of how, and when, the solar system's biggest planet formed.
Jupiter holds about twice as much mass as the rest of the solar system combined, not counting the sun. And it was the first planet to coalesce after the sun formed, gobbling up most of the dust and gas left in the early solar system.
That's part of the reason it's so interesting, according to Bolton. [Top 10 Extreme Planet Facts]
"If we want to go back in time and understand where we came from and how the planets were made, Jupiter holds the secret, because it's got most of the leftovers after the sun formed," Bolton told reporters today. "We want to know that ingredient list. What we're really after is discovering the recipe for making planets."
Juno will make a variety of observations in an attempt to determine that recipe.
For example, the spacecraft will measure the amount of water contained in Jupiter's thick, swirling atmosphere. Relatively large amounts of water might suggest that Jupiter first formed farther out in the solar system, then migrated into its present position, Bolton said.
And scientists still aren't sure if Jupiter has a solid core of heavy elements, or if it's made entirely of gas. Juno will look into that question as well, by measuring Jupiter's magnetic and gravity fields.
"Juno's prepared to be able to help constrain those answers, and help provide that information so that we can discriminate among models of how Jupiter formed and, in fact, what the history of our early solar systemwas," Bolton said.
An armored tank of a spacecraft
Juno will settle into a highly elliptical polar orbit around Jupiter in 2016, coming as close as 3,107 miles (5,000 kilometers) from the gas giant's cloud-tops.
This proximity will afford great looks at the giant planet, but it's dangerous for Juno, too. Jupiter possesses the strongest radiation environmentof any solar system body beyond the sun. So mission planners have encased Juno's sensitive instruments and electronics inside a titanium "vault" for protection.
"We're basically an armored tank going to Jupiter," Bolton said.
Jupiter's strong radiation also dictated the particulars of Juno's orbit, requiring mission managers to slot the spacecraft precisely between several dangerous belts on its laps around the planet.
"This is like threading a needle," Bolton said. "We're going right through the only safe haven."
Juno weighs about 8,000 pounds (3,627 kilograms), but about half of that is fuel, researchers said. For power, the spacecraft relies on three huge solar arrays, each the size of a tractor-trailer.
The arrays' 18,698 solar cells will generate about 400 watts of power out at Jupiter, which sits about 400 million miles (644 million km) farther from the sun than Earth does. Out there, sunlight is 25 times less intense than it is here on our home planet.
Juno will make 33 orbits of Jupiter over its year-long operational life, then be crashed intentionally into the giant planet. Researchers want to make sure Juno doesn't slam into — and contaminate — any of Jupiter's moons, some of which scientists think may be capable of supporting life.
But the mission's end is far off in the future, as are the beginnings of its observations at Jupiter. For now, the mission team is looking forward to just getting the spacecraft off the ground.
"It's really exciting," Bolton said. "We're just a few days away from our launch."
Copyright © 2011 Space.com. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed. | 0.833373 | 3.274559 |
Photos from SpaceX’s satellite launch shocked many astronomists, who are worried about their ability to study deep space.
Space observers eagerly watched last week as SpaceX launched the first round of what it says will be thousands of satellites meant to deliver fast and affordable internet to Earth.
Many were surprised at what they saw.
The first 60 of nearly 12,000 planned satellites in the Starlink project visibly lit up the sky as they travelled in a line in low-Earth orbit.
Videos of the satellites began circulating on social media, sparking alarm among astronomers who need a clear view of the sky to study deep space and already report having problems with the roughly 5,000 satellites currently in orbit.
Telescopes aimed at examining a large portion of the sky require a long exposure time. The larger the field of view, the longer the imaging will take and the more likely the picture will be littered with trails from satellites moving across the sky.
“My experience has been that even now … a significant number of the exposures you take will have a satellite streak going through,” says Phil Mauskopf, a professor at Arizona State University’s School of Earth and Space Exploration.
“I don’t think [Starlink is] going to completely ruin astronomy,” Mauskopf says. “I think you’ll still be able to do it, but I do think it will make it less efficient.”
While satellite visibility poses its own problems, another issue that we can’t see worries astronomers.
Satellites work by using radio waves to send data back to Earth. That means they produce radio frequency interference, says Caitlin Casey, an assistant professor in the University of Texas at Austin’s astronomy department.
Photos: Space Over Time
Many devices produce radio frequency interference, or RFI, Casey says. Cellphones, the radio we listen to and military communications networks are all sources.
The difference is that these devices are land-based, and Starlink’s satellites will be directly between telescopes and the distance objects astronomers want to study.
“For reference, even a single cell phone located on the surface of the moon would appear like a bright radio source contaminating the sky in its vicinity,” Casey says in an email.
Astronomers are able to study the history of the universe by examining distant gases. If the RFI gets to be too much, “it’ll potentially close our window on these critical measurements of gas in the early Universe,” she says.
When U.S. News reached out to SpaceX for comment, a company spokesperson passed along links to Elon Musk’s tweets on the topic.
The SpaceX CEO’s remarks ranged from dismissive to promising.
In response to concerns about the project, Musk tweeted that “potentially helping billions of economically disadvantaged people is the greater good” and that “we need to move telescopes into orbit anyway.”
But he also said that the project will avoid certain radio frequencies specifically for radio astronomy.
Without giving many details, Musk said “we’ll make sure Starlink has no material effect on discoveries in astronomy.”
Casey says astronomers are likely appreciative that SpaceX is listening to their concerns but adds that it shouldn’t be up to the good will of one company to protect scientific research. She says an independent assessment of the project’s impacts is needed.
Many astronomers agree that communication from SpaceX about the project was lacking.
“It seems like a problem to me that most astronomers have found out about the impact of this project through Twitter on a holiday weekend,” Casey says.
Mauskopf suggests that SpaceX look into coordinating with large telescope projects to see if it would be possible to shut off the satellites as they fly over certain areas.
“If they can’t do that, they’ll blast us,” he says.
At least one satellite doesn’t expect Starlink to pose too much of a problem.
The Large Synoptic Survey Telescope, which is being built in Chile, is meant to conduct a 10-year survey of the sky to help understand topics like dark matter and the formation of our galaxy.
An increase in the number of satellites will require some extra work from the telescope’s team, but it won’t be “catastrophic,” says Yusra AlSayyad, the telescope team’s satellite trail expert.
Once the team has completed several regional surveys, an algorithm will be able to anticipate and remove satellite trails, AlSayyad says.
Beyond Starlink, concerns are rising over the effects the intensifying satellite presence in Earth’s atmosphere might have.
One factor that is particularly concerning to stargazers is that SpaceX’s satellites are being launched into low orbit, which will help them to provide faster internet access, according to Musk. But being closer to the ground means being more visible, and several companies, including Amazon and OneWeb, have similar plans to launch more satellites to provide internet coverage.
“The number of low Earth orbit satellites planned to launch in the next half-decade has the
potential to fundamentally shift the nature of our experience of the night sky,” the International Dark-Sky Association said in a statement.
The group, which was founded in 1988 by astronomers concerned about the growing prevalence of light pollution, asked “all parties to take precautionary efforts to protect the unaltered nighttime environment before deployment of new, large-scale satellite groups.”
Caution in this area should be used since the effects aren’t fully known, it said.
“We do not yet understand the impact of hundreds or thousands of these visible satellites scattered across the night sky on nocturnal wildlife, human heritage, or our collective ability to study the cosmos,” the association said. | 0.822219 | 3.349368 |
Think the weather is nasty this winter here on Earth? Try vacationing on the brown dwarf Luhman 16B sometime.
Two studies out this week from the Max Planck Institute for Astronomy based at Heidelberg, Germany offer the first look at the atmospheric features of a brown dwarf.
A brown dwarf is a substellar object which bridges the gap between at high mass planet at over 13 Jupiter masses, and a low mass red dwarf star at above 75 Jupiter masses. To date, few brown dwarfs have been directly imaged. For the study, researchers used the recently discovered brown dwarf pair Luhman 16A & B. At about 45(A) and 40(B) Jupiter masses, the pair is 6.5 light years distant and located in the constellation Vela. Only Alpha Centauri and Barnard’s Star are closer to Earth. Luhman A is an L-type brown dwarf, while the B component is a T-type substellar object.
“Previous observations have inferred that brown dwarfs have mottled surfaces, but now we can start to directly map them.” Ian Crossfield of the Max Planck Institute for Astronomy said in this week’s press release. “What we see is presumably patchy cloud cover, somewhat like we see on Jupiter.”
To construct these images, astronomers used an indirect technique known as Doppler imaging. This method takes advantage of the minute shifts observed as the rotating features on brown dwarf approach and recede from the observer. Doppler speeds of features can also hint at the latitudes being observed as well as the body’s inclination or tilt to our line of sight.
But you won’t need a jacket, as researchers gauge the weather on Luhman 16B be in the 1100 degrees Celsius range, with a rain of molten iron in a predominately hydrogen atmosphere.
The study was carried out using the CRyogenic InfraRed Echelle Spectrograph (CRIRES) mounted on the 8-metre Very Large Telescope based at the European Southern Observatory’s (ESO) Paranal observatory complex in Chile. CRIRES obtained the spectra necessary to re-construct the brown dwarf map, while backup brightness measurements were accomplished using the GROND (Gamma-Ray Burst Optical/Near-Infrared Detector) astronomical camera affixed to the 2.2 metre telescope at the ESO La Silla Observatory.
The next phase of observations will involve imaging brown dwarfs using the Spectro-Polarimetric High-contrast Exoplanet Research (SPHERE) instrument, set to go online at the Very Large Telescope facility later this year.
And that may just usher in a new era of directly imaging features on objects beyond our solar system, including exoplanets.
“The exciting bit is that this is just the start. With the next generations of telescopes, and in particular the 39-metre European Large Telescope, we will likely see surface maps of more distant brown dwarfs — and eventually, a surface map for a young giant planet,” said Beth Biller, a researcher previously based at the Max Planck Institute and now based at the University of Edinburgh. Biller’s study of the pair went even more in-depth, analyzing changes in brightness at different wavelengths to peer into the atmospheric structure of the brown dwarfs at varying depths.
“We’ve learned that the weather pattern on these brown dwarfs are quite complex,” Biller said. “The cloud structure of the brown dwarf varies quite strongly as a function of atmospheric depth and cannot be explained with single layer clouds.”
The paper on brown dwarf weather pattern map comes out today in the January 30th, 2014 edition of Nature under the title Mapping Patchy Clouds on a Nearby Brown Dwarf.
The brown dwarf pair targeted in the study was designated Luhman 16A & B after Pennsylvania State University researcher Kevin Luhman, who discovered the pair in mid-March, 2013. Luhman has discovered 16 binary systems to date. The WISE catalog designation for the system has the much more cumbersome and phone number-esque designation of WISE J104915.57-531906.1.
We caught up with the researchers to ask them some specifics on the orientation and rotation of the pair.
“The rotation period of Luhman 16B was previously measured watching the brown dwarf’s globally-averaged brightness changes over many days. Luhman 16A seems to have a uniformly thick layer of clouds, so it exhibits no such variation and we don’t yet know its period,” Crossfield told Universe Today. “We can estimate the inclination of the rotation axis because we know the rotation period, we know how big brown dwarfs are, and in our study, we measured the “projected” rotational velocity. From this, we know we must be seeing the brown dwarf near equator-on.”
The maps constructed correspond with an amazingly fast rotation period of just under 6 hours for Luhman 16B. For context, the planet Jupiter – one of the fastest rotators in our solar system – spins once every 9.9 hours.
“The rotational period of Luhman 16B is known from 12 nights of variability monitoring,” Biller told Universe Today. “The variability in the B component is consistent with the results from 2013, but the A component has a lower amplitude of variability and a somewhat different rotational period of maybe 3-4 hours, but that is still a very tentative result.”
This first mapping of the cloud patterns on a brown dwarf is a landmark, and promises to provide a much better understanding of this transitional class of objects.
Couple this announcement with the recent nearby brown dwarf captured in a direct image, and its apparent that a new era of exoplanet science is upon us, one where we’ll not only be able to confirm the existence of distant worlds and substellar objects, but characterize what they’re actually like. | 0.865569 | 3.837493 |
For the second time in history, after 41 years on the road, NASA’s Voyager 2 spacecraft has finally reached interstellar space. NASA has confirmed that Voyager 2 exited the heliosphere which is the protective bubble of particles and magnetic fields created by the Sun.
Earlier in 2012, its twin, the Voyager 1 crossed a different path of this boundary but Voyager 2 that carried a working instrument that will provide first of its kind observations of the nature of this gateway into the interstellar space.
We are all happy and relieved that the Voyager probes have both operated long enough to make it past this milestone, Suzanne Dodd, the Voyager project manager from NASA’s Jet Propulsion Laboratory said.
Mission operators can still communicate with the Voyager 2, which is now slightly more than 11 billion miles (18 billion kilometers) from the Earth.
“This is what we’ve all been waiting for. Now we’re looking forward to what we’ll be able to learn from having both probes [in interstellar space],” Ms. Dodd said in a statement. Both spacecraft are still in regular contact with NASA‘s Deep Space Network (DSN) ground stations, including Australia.
Unlike Voyager 1, Voyager 2 has instruments set up that measure changes in the speed and direction of high energy plasma particles as the wind from our Sun meets the high energy particles streaming in from the rest of the galaxy.
The energy streaming from our own Sun is literally like a wave around the solar system, Glen Nagle of the Canberra Deep Space Communication Complex said.
- It’s the same way as a ship cutting through water creates a bow shock wave around it.
- The Voyager spacecraft are now ahead of that wave in the clear air of interstellar space.
- “Voyager 2 seems to have entered that region about 18 billion kilometers from the Sun.
Voyager 2 was launched on August 20 1977 — 16 days before its twin Voyager 1 — making it the oldest space mission.
“Its mission was to go and visit the giant planets of the solar system Jupiter, Saturn and of course eventually Uranus and Neptune,” Mr. Nagle said.
Nobody really expected the spacecraft to last this long, to be able to continue out on their journey, to travel through the heliosheath boundary, out across the heliopause into interstellar space,” It is the only spacecraft to have flown by Uranus, in 1986, and Neptune, in 1989.
Mr. Nagle said the tracking stations were talking to Voyager 2 for about 15 hours a day.”The spacecraft no longer has a working recorder on board so it is continuously streaming back that information,” the spacecraft had enough power to run science instruments until 2025. | 0.812111 | 3.183829 |
A bombardment of cosmic rays on the moon’s surface could be creating complex carbon chains similar to those that form the foundations of biological life.
According to scientists from the University of New Hampshire, galactic cosmic rays (CGRs) are releasing oxygen atoms from water ice, which are then free to bind with carbon to form large, ‘prebiotic’ organic molecules.
In addition, says the team, the radiation process causes the lunar soil, or regolith, to darken over time.
By chance, the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) team was able to make measurements during a period when cosmic ray fluxes were at the highest levels ever observed, thanks to the sun’s abnormally extended quiet cycle.
“This has provided us with a unique opportunity because we’ve never made these types of measurements before over an extended period of time, which means we’ve never been able to validate our models,” says Nathan Schwadron, an associate professor of physics at UNH.
“Now we can put this whole modeling field on more solid footing and project GCR dose rates from the present period back through time when different interplanetary conditions prevailed.”
The team believes that cosmic radiation may have been a fundamental agent of change on celestial bodies by irradiating water ice and causing chemical alterations.
Now, however, such radiation presents a hazard for astronauts, and the new observations could help minimize the risk.
“Our validated models will be able to answer the question of how hazardous the space environment is and could be during these high-energy radiation events, and the ability to do this is absolutely necessary for any manned space exploration beyond low-Earth orbit,” says Schwadron. | 0.842179 | 3.777163 |
Washboard and fluted terrains on Pluto as evidence for ancient glaciation
A letter authored by SETI Institute scientist Oliver White was published by Nature Astronomy today. Co-authors included researchers Jeff Moore, Tanguy Bertrand and Kimberly Ennico at NASA's Ames Research Center in Silicon Valley.
The letter "Washboard and Fluted Terrains on Pluto as Evidence for Ancient Glaciation" focuses on these distinctive landscapes that border the vast nitrogen ice plains of Sputnik Planitia along its northwest margin (Figure 1), and which are amongst the most enigmatic landforms yet seen on Pluto. These terrains consist of parallel to sub-parallel ridges that display a remarkably consistent ENE-WSW orientation, a configuration that does not readily point to a simple analogous terrestrial or planetary process or landform.
The aim of Dr. White's research is to use mapping and analysis of the morphometry (the process of measuring the external shape and dimensions of landforms) and distribution of the ridges to determine their origin and to understand their significance within the overall geologic history of Pluto. The work used imaging data returned by NASA's New Horizons spacecraft, which flew past Pluto in 2015, as well as topographic maps generated from this data. Washboard and fluted ridges are defined primarily by their topographic context: washboard ridges occur in level settings within valley floors, basins and uplands, whereas fluted ridges are seen on steeper spurs, massifs (or compact group of mountains) and crater walls that separate basins and valleys.
The washboard and fluted terrain is seen up close in Figure 2, in which illumination is from the top. They occur at the location on Sputnik Planitia's perimeter where elevations and slopes leading into the surrounding uplands are lowest, and also where a major tectonic system coincides with the edge of Sputnik Planitia. The low elevation of the area makes it a natural setting for past coverage by nitrogen ice glaciers, as indicated by modeling of volatile behavior on Pluto performed by Dr. Bertrand at Ames. Through comparison of the washboard and fluted texture with parallel chains of elongated sublimation pits (depressions in the surface formed where ice turns directly into a gas) seen in southern Sputnik Planitia, the ridges are interpreted to represent water ice debris liberated by tectonism of underlying crust. This water ice debris was buoyant in the denser, pitted glacial nitrogen ice that is interpreted to have formerly covered this area, and collected on the floors of the elongated pits. After the nitrogen ice receded via sublimation, the debris was left as the aligned ridges, mimicking the sublimation texture – washboard ridges where deposited on flat terrain, and fluted ridges where deposited on steeper slopes.
Crater surface age estimates indicate that the washboard and fluted ridges were deposited early in Pluto's history, after formation of the Sputnik basin by a giant impact ~4 billion years ago. Acting as a giant cold trap, it was to this basin that surface nitrogen ice across Pluto migrated over some tens of millions of years, thereby causing the recession of nitrogen glaciers from upland areas such as that now occupied by the washboard and fluted terrain. The precise mechanism that elongated the sublimation pits and defined their strikingly consistent orientation regardless of latitude or location relative to Sputnik Planitia is elusive, but is consistent with a global-scale process.
A constraint is that true polar wander solutions for Pluto (provided by co-author Dr. James Keane of Caltech) indicate that the ridges can never have all been oriented N-S at any time in Pluto's history. This suggests a cause for the alignment that is not exogenic (i.e. the orientation is likely not governed solely by solar illumination, which would cause all the sublimation pits to align N-S). Dr. White summarizes the findings as follows: "These terrains constitute an entirely new category of glacial landform that is unique to Pluto, and represent geological evidence that nitrogen ice glaciation was more widespread across Pluto in its early history prior to the formation of the Sputnik basin. The dense spacing of the ridges allows us to precisely map out the past coverage of the glaciation that deposited them, which extended across at least 70,000 km2 of Pluto's uplands (larger than the state of West Virginia)". | 0.8933 | 3.824277 |
Olivier Hainaut tells us about a visitor from outside our Solar System
- The story of the discovery of the first interstellar asteroid
- How ESO’s telescopes are used to make rapid follow-up observations
- The process behind new and exciting scientific discoveries
Q: Tell us about how it all began. At what moment did you realise this was such an exciting discovery?
A: It all started with a short and cryptic email from my long-time friend and collaborator from Hawaii, Karen Meech, with “URGENT’’ in the subject line, telegraphic style. The main text was filled with words like discovery and immediate follow-up. Needless to say, I called her — the 12 hour time difference between Hawaii and Germany is not that bad, especially as Karen is a very early morning person and I tend to be more of an evening guy. Karen was jumping up and down: our friends at the Pan-STARRS telescope had discovered a moving object. This happens every night — Pan-STARRS discovers many comets and asteroids — but its orbit was found to be hyperbolic, which had never happened before. This meant that the object is not orbiting the Sun. We already knew a few comets with just barely hyperbolic orbits, probably caused by interactions with planets or the jet-like effect of the cometary activity, but apart from these exceptions, all known comets and asteroids are bound to the Sun and orbit around it on elliptical paths. All except this one.
That definitely deserved the “URGENT” email: this object is zooming past the Sun and heading away from the Solar System, forever — and fast.
Q: After the initial discovery, what was the next step?
A: The next day, we slammed together a request for telescope time to observe the object while we could. Normally, these requests have to be written six months to a year in advance, but fortunately there’s a super-fast-track way to apply for time in emergency cases. The request was submitted to ESO, reviewed by other astronomers (who became almost as enthusiastic as us!), and the director approved it — all within just a few hours.
In the meantime, I’d already started to prepare the observations — that is, to define all possible details of the exact sequence of images we needed, taking into account that the object is moving very fast in the sky. As soon as I was notified that we’d been allocated telescope time (a few hours on UT1, one of the Very Large Telescope’s 8.2-m telescopes), I uploaded the observation definitions to the telescope database. That night, my colleagues working at the Paranal Observatory performed the observations and quickly sent the images to Germany, where I looked at them in the morning.
Q: So what did the images show?
A: Images coming straight from the telescope are not pretty. Not only are they in greyscale (the beautiful images of space you are used to seeing are assembled from various greyscale images obtained through colour filters), but they also have all kinds of odd features produced by the camera that need to be corrected. I spent the morning processing the images, which were excellent. First conclusion — this is not a comet!
We have been expecting interstellar objects for many years — we know that our Solar System has been ejecting comets and asteroids into interstellar space for the past 4.5 billion years. If our neighbouring stellar systems do the same, interstellar space should be full of these objects, so we believed it would be just a matter of time before we bumped into one. Except that most of these interstellar objects should be comets, and comets are much easier to spot than asteroids, so we had expected to first spot an interstellar comet! The object we discovered was most definitely not a comet: it didn’t have the faintest hint of dust around it, as would be expected. Combining all our data from the Very Large Telescope (VLT) observations, we produced a very deep image, from which I measured that there is less than a gram (!) of dust in each pixel around the object.
Q: What were you thinking when you realised this object wasn’t a comet?
A: At that stage, it was impossible not to draw parallels with the great sci-fi novel “Rendezvous with Rama” by A. C. Clarke, in which astronomers discover an object in a hyperbolic orbit crossing the Solar System — and it is not a comet. In the book, the object’s brightness is extremely stable, but because asteroids normally have irregular shapes, they appear brighter and dimmer as they rotate, alternately exposing their larger and smaller sides to us. So a constant brightness is not normal; in the novel, the object turns out to be a giant starship, which the heroes go on to explore. Reality was quite different.
Q: How so? What did you find out about the object?
A: As we collected more data with the VLT, in conjunction with Gemini (another 8-m telescope) and the Canada-France-Hawaii telescope (a “small” 3.6-m telescope), we realised the brightness of our interstellar object was varying a lot. Actually, by a factor of 10, which is close to an absolute record.
The lightcurve of the object (the variation of brightness with time) gave us a lot of information. Firstly, we found the rotation period to be 7.3 hours, which is fairly standard for an asteroid. Secondly, while we don’t know the exact shape, we can infer that its “large” side is at least 10 times longer than its “small” side. We don’t know how thick the asteroid is, but we can guess using good old basic physics: as the lightcurve is nice and regular, the object must be gently rotating and not tumbling uncontrollably. This implies it is rotating around its smallest dimension, as demonstrated by Euler in the eighteenth century, so we’re dealing with a long cigar-shaped object, twirling like a cheerleader’s baton.
By measuring the amount of sunlight reflected by the object, it is also possible to make educated guesses about its length, depending on the darkness of the surface. In this case, our object is a few hundred metres long. Knowing the size and the rotation period, we computed the centrifugal force at the tip of the asteroid and estimated the strength of gravity on the surface. It turns out that if you were to stand on the tip of the spinning asteroid, you’d be ejected in space: the centrifugal force is stronger than the gravity! This, in turn, implies that the object is one solid piece of rock.
Finally, as we observed the object through different colour filters we measured that its surface is reddish, like the surface of some “old” asteroids and comets in our own Solar System.
So the first interstellar object crossing the Solar System is full of surprises: it is not comet, it’s a solid piece of rock with an extreme shape! But at least its surface is familiar-looking. This suggests that the interstellar object is not that exotic: asteroids in our Solar System and in other solar systems have things in common.
Q: Now that you’ve discovered and characterised the asteroid, what’s next?
A: We’re going to keep observing it for as long as we can, using the VLT and the Hubble Space Telescope, but by the end of the year, it will be too far from us and from the Sun and therefore too faint to be observed. Forever. Unless we send a send a spacecraft after it...
Numbers in this article
|1||Number of known interstellar asteroids (as of 15 Nov 2017)|
|948||Number of known comets (as of 15 Nov 2017)|
||Number of known asteroids (as of 15 Nov 2017)|
Biography Olivier Hainaut
Olivier Hainaut is an astronomer working on comets and asteroids. He has previously worked at ESO’s Paranal Observatory, and before that at the La Silla Observatory, but is now back at ESO Headquarters in Germany. Email: [email protected] | 0.936634 | 3.677928 |
Astronomers have spotted water vapor and evidence of exotic clouds in the atmosphere of an alien planet known as HAT-P-26b.
The researchers also determined that HAT-P-26b's atmosphere is dominated by hydrogen and helium to a much greater degree than that of Neptune or Uranus, the alien world's closest counterparts in our own solar system in terms of mass.
"This exciting new discovery shows that there is a lot more diversity in the atmospheres of these exoplanets than we have previously thought," David Sing, an astrophysics professor at the University of Exeter in England, said in a statement. [Gallery: The Strangest Alien Planets]
"This 'warm Neptune' is a much smaller planet than those we have been able to characterize in depth, so this new discovery about its atmosphere feels like a big breakthrough in our pursuit to learn more about how solar systems are formed, and how it compares to our own," added Sing, the co-leader of a new study about HAT-P-26b that was published online today (May 11) in the journal Science.
Water and alien clouds
HAT-P-26b lies about 430 light-years away from Earth. The alien planet circles very close to its host star, completing one orbit every 4.2 Earth days. This proximity suggests that HAT-P-26b is tidally locked, showing the same face to its star at all times, said Hannah Wakeford, co-leader of the new study and a postdoctoral researcher at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
Sing, Wakeford and their colleagues analyzed observations made by NASA's Hubble and Spitzer space telescopes when HAT-P-26b crossed its parent star's face from the telescopes' perspectives. The planet's atmosphere filtered out certain wavelengths of starlight during these "transits," allowing the study team to identify some of the molecules swirling in HAT-P-26b's air.
One such molecule is water.
"For this mass range, this is the strongest water-absorption feature that we have ever measured," Wakeford told Space.com.
The data also indicate that clouds scud across HAT-P-26b's skies, but relatively deep in the atmosphere; they do not block much of the water-absorption signal, Wakeford said. These clouds are probably made of disodium sulfide, not water vapor like those of Earth, she added.
"This would be a very alien sky that you would be looking at," Wakeford said. "These clouds would cause scattering in all of the colors, so you'd get a kind of scattery, washed-out, gray sky, which is interesting, if you were looking through these clouds."
Ultrabright light streaming from the nearby star would bombard an observer above the clouds, she added. "There's nothing there to really help stop that sunlight from reaching you."
Clues about planet formation
Using the transit data, the study team also calculated the "metallicity" of HAT-P-26b's atmosphere — how much of it is made up of elements other than hydrogen and helium. (To an astronomer, anything heavier than helium is a metal.)
In Earth's solar system, metallicity goes down as a planet's mass goes up. For example, Neptune and Uranus both have metallicities about 100 times greater than that of the sun (which is almost entirely hydrogen and helium), whereas the much larger Saturn and Jupiter are just 10 and five times more metallic than the sun, respectively.
But HAT-P-26b does not fit that pattern. Though the exoplanet is about as massive as Neptune, its metallicity is more in line with that of Jupiter, the researchers in the new study found.
This surprising bit of information holds clues about HAT-P-26b's formation and evolution, Wakeford said.
"It suggests that this smaller planet actually formed closer to its star, more like where Jupiter formed," she said. "And we didn't know before that you could form [such] planets in that region. We expected the smaller worlds to be formed further out, where they would accumulate clumps of icy debris and richer heavy elements during the formation in the [protoplanetary] disk." (In these scenarios, planets such as HAT-P-26b migrate inward, toward their stars, after they form.)
Over the last decade or so, NASA's Kepler space telescope and other planet-hunting instruments have revealed a staggering array of alien worlds and solar system architectures. The new study, and others like it, should help researchers better understand the reasons for this variety, Wakeford said.
"This is the first step toward looking at the diversity in the formation process as well," she said. | 0.889196 | 3.726059 |
Deep Space Dust Busters
A USF astrophysics team sweeps away intergalactic "fog"
A USF astrophysics team’s research into space dust paves the way for scientists to better understand how the universe evolves.
Professor Xiaosheng Huang and students Zachary Raha ’16 and Andrew Stocker ’15, along with a scientist at Lawrence Berkeley National Laboratory, came up with an innovative computer model that accounts for interference caused by interstellar dust surrounding a faraway supernova, or exploding star.
Scientists use supernovae brightness to measure great distances in space. Dust can obscure supernovae light — similar to the way fog dims an oncoming headlight. The USF team’s model effectively wipes away the fog, allowing the team to more accurately measure the distance from our Milky Way galaxy to the supernova’s galaxy.
A first for science
“It’s the first time scientists have applied this kind of computer algorithm to supernova spectra to eliminate interference from dust, in order to better measure distances,” says Huang, who teaches physics and astronomy.
Being able to more accurately measure great distances in space is key to helping scientists understand why the universe is expanding at an accelerated rate, and how the universe has evolved since the Big Bang, Huang says.
The USF team’s work was published earlier this year in The Astrophysical Journal, the field’s premier academic journal.
Huang, leader of the project, was first author on the research paper, which drew on supernovae data collected by an international group of scientists. Raha, who worked with Huang for three summers, was credited as second author — a prestigious distinction for an undergraduate.
“It was rewarding to see the two students grow,” Huang said. “And they helped me clarify my thinking. They asked good questions.”
Learning from a Nobel laureate
For Raha, who majored in physics, the research was an introduction to the world outside the classroom.
“In school you get used to textbooks, where you’re able to extract information because it’s easily laid out for you,” says Raha. “But we were reading technical research papers. It’s different because scholars are usually only writing for members of their own community, so it takes little bit more getting used to.”
After graduation Raha completed an internship at Lawrence Berkeley National Laboratory, working with Nobel laureate physicist Saul Perlmutter on another supernovae research project.
“After my internship I’ve become a lot more sure that astrophysics research is a career I want to pursue,” he says. “I’m hoping to apply for graduate school next. I’m really excited about having this career where I can basically learn for a living.”
Stocker, a math major who worked on the project for one summer before graduating, is completing a doctorate in math at the University of Colorado Boulder. | 0.86929 | 3.710389 |
Evidence for solar-production as a source of polar-cap plasma
The focus of the study is a region of enhanced ionospheric densities observed by the EISCAT Svalbard radar in the polar F-region near local magnetic noon under conditions of IMF
Bz<0. Multi-instrument observations, using optical, spacecraft and radar instrumentation, together with radio tomographic imaging, have been used to identify the source of the enhancement and establish the background ionospheric conditions. Soft-particle precipitation was ruled out as a candidate for the production. Tomographic observations identified a latitudinally restricted region of enhanced densities at sub-auroral latitudes, distinct from the normal mid-latitude ionosphere, which was likely to be the source. The evidence suggested that the increased sub-auroral densities were photoionisation produced at the equatorward edge of the afternoon high-latitude cell, where the plasma is exposed to sunlight for an extended period as it flows slowly sunward toward magnetic noon. It is proposed that this plasma, once in the noon sector, was drawn antisunward by the high-latitude convection toward polar latitudes where it was identified by the EISCAT Svalbard radar. The observations are discussed in terms of earlier modelling studies of polar patch densities.
Key words. Ionosphere (polar ionosphere; plasma temerature; plasma convection) | 0.817599 | 3.088622 |
This article summaries the planetary activity in the evening sky during 2018. The articles that follow provide details about the planets visible without optical assistance (binoculars or telescope):
- Chart and Image Collection
- 2018: The Morning Sky
- 2018: The Evening Sky
- 2018: Mercury in the Morning Sky
- 2018: Mercury in the Evening Sky
- 2018: Five Planets Visible at Once
- 2018: Venus the Evening Star
- 2017-2019: Mars Observing Year with a Perihelic Opposition, July 27, 2018
- 2018: Mars Perihelic Opposition
- 2017-2018: Jupiter’s Year in the Claws of the Scorpion, A Triple Conjunction
- 2018: Three Planets at Opposition in 79 days
- 2018: Saturn with the Teapot
The chart shows the setting of planets, stars, and the moon (circles) compared to sunset. This occurs in the western sky. The three phases of twilight are graphed as well.
Conjunctions are displayed with squares. Yellow triangles and the letters “GE” show the greatest elongation of Mercury or Venus. A yellow diamond with the letters “GB” indicate the interval of Venus’ greatest brightness.
The rising of Mars, Jupiter, and Saturn are displayed. This occurs in the east. The opposition dates of those planets are also indicated.
It is important to emphasize that the chart shows setting times. When the setting lines of two objects cross, it indicates that they set at the same time. Because we have chosen planets and stars along the ecliptic, the virtual path along which the sun, moon and planets appear to move along, they can appear at conjunction or near each other. This can occur within a few days of the date of coincident setting. For the purposes of the chart, the conjunction is indicated on the setting time curve of the brighter planet. When considering planets setting at the same time, consider this: Sirius, the brightest star in the night sky, sets at about the same time as Aldebaran in Taurus. The stars, though, are 46 degrees apart in the sky. Sirius sets in the southwest and Aldebaran sets in the west-northwest.
The charts below summarize some of the evening events during the year. This includes oppositions of Jupiter, Saturn, and Mars. Just before the opposition of Mars, the five naked eye planets can be seen at once. Observers at more southerly latitudes see this event easier.
Jupiter and Venus do not have a conjunction. At the end of September the planets are closest at 14 degrees. | 0.871234 | 3.638972 |
A decade from now, NASA probes could be on their way to explore two potentially life-supporting alien worlds.
The agency already plans to launch a spacecraft toward the Jupiter moon Europa in the early to mid-2020s, and it's mulling a mission to the Saturn satellite Enceladus that would lift off by the end of 2021. Many astrobiologists regard Europa and Enceladus, which are both thought to harbor oceans of liquid water beneath their icy shells, as the solar system's two best bets to host alien life.
The possible Encelacus project, known as the Enceladus Life Finder (ELF), is one of two dozen or so concepts submitted earlier this year for consideration by NASA's Discovery Program, which launches highly focused, relatively low-cost missions to various solar system destinations. [Inside Enceladus, Icy Moon of Saturn (Infographic)]
NASA is expected to cull the original Discovery applicant pool to a handful of finalists next month, then select the overall winner around September 2016. The people behind ELF — which, as its name suggests, would search for signs of biological activity on Enceladus — believe they've put forward a strong contender.
"We think we have the highest chance of success of getting an indicator of [alien] life for really any mission at this point," ELF concept principal investigator Jonathan Lunine, of Cornell University, told Space.com.
Going to Enceladus?
In 2005, NASA's Saturn-orbiting Cassini spacecraft spotted geysers of water ice, salts, carbon-containing organics and other molecules erupting from the south polar region of the 310-mile-wide (500 kilometers) Enceladus.
These jets, which are powered by Saturn's intense gravitational pull, merge to form a plume that reaches far out into space. Indeed, Enceladus supplies the bulk of the material making up Saturn's wide E-ring.
Scientists think the icy jets are in contact with Enceladus' underground ocean, which offers a rare and tantalizing opportunity — gathering samples from a potentially habitable alien environment without even touching down. (Furthermore, the oceans of Europa and Enceladus lie beneath miles of ice, which could make sampling by a landed mission tough.)
That's just what ELF intends to do.
"It's free samples," Lunine said of the plume. "We don't need to land, drill, melt or do anything like that." [Enceladus' Surprising Geysers (Video)]
Cassini has flown through the plume multiple times, but that spacecraft isn't equipped to search for life. ELF, on the other hand, would probe the habitability of Enceladus' ocean and hunt for evidence of biological activity.
ELF would carry two mass spectrometers; one would be optimized to study gaseous plume molecules, whereas the other would focus on solid grains, Lunine said. These instruments would study amino acids (the building blocks of proteins), fatty acids, methane and other molecules, allowing mission scientists to perform three separate tests for life.
"Positive results for all three would strongly argue for life within Enceladus," the ELF team wrote in a paper presented at the 46th Lunar and Planetary Science Conference, which was held in March in The Woodlands, Texas.
"ELF brings the most compelling question in all of space science within reach of NASA’s Discovery Program, providing an extraordinary opportunity to discover life elsewhere in the solar system in a low-cost program," they added. (Whichever mission is selected for this Discovery round will have a cost cap of $450 million, excluding post-lauch operations.)
A fourth life test should also be possible, Lunine said. Current ELF plans call for including a technology-demonstration instrument designed to determine the chirality, or "handedness," of amino acids. All Earth life uses left-handed amino acids rather than right-handed ones; a similar preference found in an extraterrestrial sample would be a strong indication of alien life, astrobiologists say.
If NASA chooses ELF, the mission will by ready by 2020 and could launch that year or in 2021, Lunine said. The baseline concept calls for ELF to launch aboard a United Launch Alliance Atlas V rocket and endure a 9.5-year-long journey to Saturn (though the trip would be much shorter if NASA's Space Launch System megarocket, which is currently in development, were used).
ELF would enter orbit around Saturn, then fly through Enceladus' plume eight to 10 times over the course of three years. These sampling sojourns would bring the robotic probe within about 31 miles of Enceladus' surface, Lunine said.
ELF is a logical follow-on from Cassini and leverages much of the older mission's heritage, he added. But the two are far from carbon copies. The school-bus-size Cassini, for example, cost $3.2 billion and features 12 onboard instruments.
Cassini is also powered by three radioisotope thermoelectric generators (RTGs), which convert the heat of plutonium-238's radioactive decay into electricity. But ELF would be solar-powered, because NASA, concerned about its dwindling stockpile of plutonium-238, prohibited the use of nuclear fuel for this Discovery mission.
No solar-powered spacecraft has ever operated as far away as Saturn, where sunlight is considerably weaker than it is here on Earth. NASA's Juno probe, in fact, will make history as the first solar-powered Jupiter spacecraft when it reaches the solar system's largest planet next July.
But Lunine is confident that solar energy will do the job for ELF.
"We found that this was a very feasible way to conduct the mission," he said, declining to provide technical details because the Discovery competition is ongoing.
Demonstrating the utility of solar power at Saturn is an important goal in itself, Lunine added, because nuclear fuel will always be in relatively short supply and therefore reserved for future missions that cannot do without it. Examples of plutonium-dependent missions include efforts to explore the surface or atmosphere of Saturn's huge, haze-shrouded moon Titan or probes that journey to extremely faraway destinations such as Neptune.
"We want to push the boundaries for solar power so that, for missions in orbit around Saturn, we don't need to use that valuable inventory of radioisotopic fuel that's going to be needed for these other missions," Lunine said.
NASA's upcoming Europa mission, which does not have an official name at the moment, will also make use of solar power. The roughly $2 billion mission will be based in orbit around Jupiter but will make 45 flybys of the 1,900-mile-wide Europa over the course of two and a half years or so.
The Europa probe will carry cameras, a heat detector, ice-penetrating radar and a variety of other instruments to gauge the habitability of the Jovian moon. But it's not designed to search for signs of life; NASA officials have expressed hope that the Europa flyby mission could help pave the way for a future landed effort that would get beneath the moon's ice shell. [Europa: Jupiter's Icy Moon and Its Underground Ocean (Video)]
Other Enceladus efforts
Lunine and his group aren't the only scientists interested in exploring Enceladus.
For example, another team has been working on a idea called Journey to Enceladus and Titan (JET), which would assess the life-supporting potential of both moons. And another research group is developing a mission concept called Life Investigation for Enceladus (LIFE), which would return samples from the icy satellite's plume back to Earth for analysis.
Neither JET nor LIFE was proposed as part of the most recent Discovery call. The LIFE team dropped out of the running primarily because it viewed nuclear power as more or less a necessity for a Saturn mission, leader Peter Tsou told Space.com.
But Tsou and his colleagues continue to work on LIFE and hope to submit the concept during a future NASA call for proposals.
Enceladus is more than worthy of the attention it's currently getting, said Tsou, who's based at Sample Exploration Systems in La Canada, California. A life-hunting mission to the geyser-spewing moon would deliver impressive "bang for the buck" astrobiologically, allowing humanity to take a solid crack at perhaps the biggest mystery facing humanity, he said.
"This 'are we alone' question — potentially we can shed tremendous light on it in a single mission," Tsou said. | 0.867024 | 3.536326 |
Mariner 10's three flybys of Mercury in 1974 and 1975 produced much of what we know about the smallest rocky planet in the system. The densely packed, lightweight spacecraft contained a variety of instruments, including TV cameras that took shots of more than half of Mercury's surface and sent back thousands of images. Mariner 10 was the first spacecraft to visit Mercury as well as the first spacecraft to send back 100-meter-resolution images from another planet. But Mariner 10 was plagued with problems: As the ship approached Mercury, one of its antennas started going through an erratic fail-heal cycle. Five weeks before the second flyby, a tape recorder failed, which meant that no data could be stored, and all of Mariner 10's data had to be sent back immediately or be lost.
Thirty years later, NASA's Messenger mission ups the ante as it becomes the first spacecraft to orbit Mercury--and takes pictures of the regions unseen by Mariner 10. Messenger boasts better tech, like the Mercury Dual Imaging System, or MDIS, which was used to produce this intimate picture. The MDIS includes a wide-angle-lens color camera that can produce images with 2000-meter-per-pixel resolution and a narrow-angle monochrome camera with 500-meter-per-pixel resolution. The dual cameras worked together to produce this intimate view of Mercury, which comes from Messenger's most recent flyby of the planet in October of this year. For reference, that crater in the middle of the picture is about 250 kilometers (155 miles) across.
Here is Venus's surface, as seen from the panoramic telephotometer aboard the Soviet Venera 10 Lander. In its 53-minute life span--measured from when it landed on the surface to the time it succumbed to the 450-plus-degree heat--the Venera 10's optical-mechanical camera snapped pictures (at a resolution of 128 x 512 pixels) and showed that, at least at that moment, the planet was extraordinarily cloudy. But Venera's black-and-white, limited shots, and its preliminary investigations of Venus's cloud cover, barely hinted at the harsh weather that a future mission would measure.
The south pole is at the bottom and the equator is at the top in this infrared and ultraviolet image of Venus from the European Space Agency's Venus Express last year. The Venus Express, launched in November 2005, reached Venus in April 2006 and has been reporting from orbit ever since. The Venus Express has already found lightning in the noxious atmosphere, sent back weather maps of the planet's surface and atmosphere and bewildered scientists with images of a double vortex at the south pole.
This influential photo, taken by Apollo 8 astronauts in December 1968, changed the view that humans had of Earth. It led us to view our planet as a small, even fragile ecosystem.
Earth Rise gave us a sentimental big picture, but since then we've been able to spot more than just hurricanes and cloud cover. Here is the latest imagery from the host of NASA's Earth-observing satellites, which measure everything from orbiting space debris to light pollution to drought. This image, taken by the Advanced Spaceborne Thermal Emission and Reflection Radiometer on board NASA's Terra satellite, shows the extent of fire damage around Los Angeles.
In July 1976, the Viking 1 lander touched down on the Mars--the first vehicle to do so successfully. Viking 1 carried instruments to take photos, measure seismic activity and get elementary weather reports. Advanced as it was for the time, Viking 1's observations left many unanswered questions about Martian history--including whether or not there was water or life.
Thirty years later, the Mars Phoenix Lander arrived on the Red Planet equipped with an onboard meteorological laboratory, a 1-megapixel Surface Stereo Imager and a gas analyzer. This image shows sublimation (when a solid vaporizes into a gas without becoming liquid) and is the first glimpse of Martian ice. In the left picture, titled Sol 20, there are tiny, dust-coated ice cubes in the bottom-left part of the frame. They almost look like rocks, except that in the next image--titled Sol 24--they're gone, like a Martian version of dry ice.
Voyagers 1 and 2 both flew by Jupiter in 1977, and between them they found three new moons and a ring--as well as proof of volcanic activity on Jupiter's moon Io. At the time, Voyager I had the highest data transmission rate of any spacecraft--21,600 bits per second--although between its trajectory and its rudimentary (by today's standards) camera, it couldn't get better than a resolution of 20 km for Jupiter.
Blink and you miss it. Thanks to telescope upgrades, like the brand-new Wide Field Camera 3 that took this picture and can take pictures in infrared, ultraviolet and visible parts of the spectrum, we can watch Jupiter in real time from the comforts of Earth. In July 2009, in the first observation after Hubble's mid-May repair, engineers aimed the Hubble Space Telescope at Jupiter to observe worlds in collision: This new dark spot on Jupiter's surface shows the impact of an asteroid and changes day to day. We may not get the same resolution as we would by taking pictures in Jupiter's backyard, but the Hubble can look at Jupiter anytime--not just when it's passing by.
Thirty years ago, this iconic portrait was our best view of Saturn. It was taken on Sept. 1, 1979, by Pioneer 11's photopolarimeter, which scanned across an area and recorded brightness, pixel by painstaking pixel--not unlike old television cameras.
How times have changed. Cassini, the largest interplanetary spacecraft ever built, has sent back some of the most dazzling photographs of the solar system that Earthlings have ever seen. The spacecraft carries dust analyzers and two cameras--the more sensitive of which could take a picture of a quarter from 2.5 miles away. On Nov. 30 it is scheduled to begins its 122nd looping, elliptical trip around the planet.
We knew almost nothing about Uranus until 1977, when astronomers suspected there were rings around it; they had been detected by telescopes as a blink when the planet passed between the Earth and a distant star. By 1986, Voyager 2 made it to Uranus and confirmed rings, along with a slew of other data, including the length of a day--17.24 hours.
While we have not sent a probe back to Uranus, the Wide Field Planetary Camera 2 on board the Hubble Space Telescope has told us much more than Voyager 2 ever could. This picture, taken in 2007, shows fully visible rings around Uranus. This is a rarity, since the rings of the planet are only visible edge-on every 42 years or so.
In 1977, astronomers predicted partial rings around Neptune, detected by telescopes when Neptune passed between the Earth and a distant star. But they weren't sure until 1989, when Voyager 2 beamed back photographic proof of multiple rings encircling the planet.
Thanks to the Hubble Space Telescope, we now know that Neptune not only has rings, but also bright clouds of icy methane and, according to infrared images captured by Hubble, changing seasons. It also has at least 13 moons. These three shots show the satellites in motion. | 0.866039 | 3.656691 |
Figure 1: One of the high school students measuring the GTT60's TFOV using Vega (Alpha Lyrae)
In the past two years already quite a few topics have been covered by the students:
Topics of research in 2018
These projects had varying outcome. Determining the orbital period of Io resulted in an incorrect figure as only two images (of 6 provided) were used in the process and the students did not realise that Io was in front of Jupiter instead of behind (it had thus not made a full number of turns).
- Determining the orbital period of Jupiter's moon Io;
- Determining the distance Sun - Venus and Sun - Pluto;
- How to make colour images using a monochrome camera;
- Determining the true and apparent field of view of the Galilean-Type Telescope.
The distance Sun - Venus, Sun - Pluto project resulted in an impressive paper, even though no actual data was hot due to weather limitations. Observational data was acquired from Stellarium instead.
The group working on the colour image using a monochrome camera managed to produce a pretty image of Saturn.
Finally the last group did a pretty good job, together with myself as third observer, to determine the true and apparent field of view of the Galilean Telescope. Adjacent image shows one of the students behind the GTT60.
Topics of research in 2019
Figure 2: The orbits of Titan and Rhea based on 13 images, covering almost 2 months.
As in 2018 the results of 2019 varied. Having learned from past year I provided the students with a better explanation how to solve the orbital parameters, now based on pictures of Saturn's moon Rhea. As I wanted to be sure that finding a solution was feasible, I did the same myself and included Titan in the calculations. Adjacent image shows my own processing, but that did not differ much from what the students achieved. Correcting for the change in distance between Saturn and Earth during the two months that 13 images were recorded, allowed to calculate the orbital period of Rhea with an error of only 9 seconds (true orbital period is 108.4320 hours, calculated period was 108.4296 hours). That of Titan was less successful, but with an error of 6 minutes, 43 seconds on a period almost 383 hours, still quite reasonable.
- Determining the orbital period of Saturn's moon Rhea;
- Determining the apparent diameter of the sun and the actual size of a solar flare;
- How to make planetary images using a colour camera and ADC;
- Determining the diameter and depth of the Tycho-crater on the Moon;
- Observing an exoplanet transit.
Processing an image of the Sun with a solar flare and calculating the Sun's diameter and the dimensions of the solar flare was well done.
The determination of the diameter and depth of the crater Tycho on the Moon, resulted again in an impressive paper with some smart maths. The result only deviated by 0.1 percent in diameter (84.9km vs 85km) and 2.8% in depth (4.57km vs 4.70km).
Due to persistent bad weather ever since the students started the exoplanet project could not be done at InFINNity Deck. Instead a dataset was provided from a Spanish Amateur, but so far no results have been shown.
If you have any questions and/or remarks please let me know. | 0.869935 | 3.609112 |
NASA’s released spectacular photos on Friday showing planet Jupiter like never seen before, providing a treasure trove to scientists to learn more about the formation of Gas Planets and offering a look deep into the Solar System’s past.
The images were acquired last weekend when the Juno spacecraft made its first orbital pass over Jupiter’s cloud tops, delivering the first-ever high resolution photos of the Gas Giant’s polar regions and close-ups of the planet’s powerful auroral display.
Juno’s 2.6-billion Kilometer journey through the Solar System that started back in August 2011 reached its destination on July 4 when the spinning spacecraft fired its engine to be captured in a highly elongated orbit around Jupiter – taking 53.5 days for one lap around the planet.
Known as the Capture Orbit Phase, Juno will complete a pair of these highly elliptical orbits before spiraling down into a shorter 14-day science orbit in October. These two longer orbits were inserted into the flight profile to provide the Mission Team with time to prepare for Juno’s busy science mission and allow for one close orbital pass to act as a rehearsal for science operations, most of which occur in the six hours centering the closest approach of the spacecraft.
Last Saturday, Juno passed within 4,200 Kilometers of Jupiter’s cloud tops, approaching the planet on a north-to-south trajectory to first overfly the north pole, reach its closest distance near the equator and then head back out flying over the south pole.
In the process, Juno exercised its eight science instruments to collect spectral data, measure Jupiter’s microwave emissions, monitor energetic particles and their motion along the planet’s magnetic field lines, measure Jupiter’s magnetic field and plasma emissions, and collecting photos with JunoCam, the mission’s sole educational payload.
A single JunoCam photo from a distance of over 700,000 Kilometers was released earlier in the week and NASA delivered on its promise of publishing additional photos later in the week.
Downlinking 6 megabytes of data from the close flyby took one and a half days using NASA’s Deep Space Network.
Scientists were eager to get their hands on the data to get their first look at what Jupiter has to offer while also verifying Juno’s instruments were up and running and ready for 20 months of exploration.
“First glimpse of Jupiter’s north pole, and it looks like nothing we have seen or imagined before,” said Juno Principal Investigator Scott Bolton. “It’s bluer in color up there than other parts of the planet, and there are a lot of storms. There is no sign of the latitudinal bands or zone and belts that we are used to — this image is hardly recognizable as Jupiter. We’re seeing signs that the clouds have shadows, possibly indicating that the clouds are at a higher altitude than other features.”
The boundary seen in the image to the right may be the result of a difference in temperature between the atmospheric zone near the pole and toward the equator.
The darker region near the pole is littered with storms of a deformed appearance but still resembling the shape of cyclones seen on Earth. Juno will be able to track the motion of these storms over multiple orbits to gain a better understanding of the dynamics at work in Jupiter’s atmosphere.
Juno orbits Jupiter in a high-inclination orbit, allowing it to fly over the polar regions. All previous Jupiter flybys and the Galileo orbiter have used equatorial trajectories that did not provide any views of the poles.
JIRAM – the Jovian Infrared Auroral Mapper – delivered its first look at the powerful aurora already seen on Jupiter using Earth-based telescopes. A close-up released on Friday provides an unprecedented view of Jupiter’s southern aurora with very bright and structured features in the infrared band. JIRAM also detected puzzling hot spots on the north and south poles that have not been seen in remote studies of the planet.
Juno’s Waves instrument was able to capture the ghostly sounding radio waves that have been known since the 1950s but were never analyzed from close by. These signatures are suspected to be coming from the same energetic particles that create Jupiter’s bright auroras, but Juno will complete a close study to find out where the electrons originate from.
Juno is currently headed back out to a distance of eight million Kilometers as part of its second capture orbit which is dedicated to all preparations for the planned October 19 Period Reduction Maneuver – a critical main engine burn to deliver Juno to its planned science orbit.
The spacecraft will pass the high point of its orbit on September 23 and then head back in, deactivating all instruments to avoid any disturbances during the main engine maneuver that will closely resemble the July 4 Orbit Insertion Maneuver: Juno will point away from the sun and Earth, begin sending status tones, face its engine towards the direction of travel and fire to slow the spacecraft down. Operational science measurements are hoped to start on November 2 when Juno will again pass Jupiter at close distance with all instruments up and running. | 0.807904 | 3.399516 |
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Curious facts about cosmic life and their inhabitants.
Have you ever wondered what may be the purpose of the moon? Well, the moon is the shiny beacon that lights up the night as the sun lights up the day. This amber body is quite shy and doesn't always show itself, but when it does, the moon's brilliance overpowers the darkness. The surface of the moon inspires astronomers around the globe who religiously watch as our incandescent orb passes serenely through its natural cycle, but if you are an avid planet observer you will come to realise that the reflecting light from the moon through the telescope lens may interfere with your ability to clearly view even our closest planets. For this reason many planet watches believe the new moon cycle is the perfect time to catch a glimpse of another world.
and here is another
GRAIL has also generated new maps showing lunar crustal thickness. These maps have managed to uncover still more large impact basins on the near-side hemisphere of Earth's Moon--revealing that there are fewer such basins on the far-side, which is the side that is always turned away from Earth. This observation begs the question: How could this be if both hemispheres were on the receiving end of the same number of crashing, impacting, crater-excavating projectiles? According to GRAIL data, the answer to this riddle is that most of the volcanic eruptions on Earth's Moon occurred on its near-side hemisphere.
Life as we know it depends on the presence of three ingredients: liquid water; a source of energy for metabolism; and the right chemical ingredients, mainly carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. With this new discovery of the existence of hydrogen, in the tattle-tale plume shooting out from the surface of Enceladus, Cassini has revealed to the prying eyes of curious astronomers, that this small, icy moon has almost all of these ingredients important for habitability. At this point, Cassini has not detected the presence of phosphorus and sulfur in the hidden subsurface ocean of this distant small world, but many planetary scientists suspect that they will eventually be detected because the rocky core of Enceladus is believed to be similar to certain meteorities that contain these two critical elements.
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Pulling it all together. The good news is, even if you and your partner do not seem connected on a deep psychic level, it's possible to strengthen this aspect of your relationship by studying and understanding your Moon chemistry. Books, astrologers, and most professional psychics can offer key insights into the magic and mystery of the Moon, and how it relates to your love life. Simply being aware of the Moon's phase, and gazing up at the Moon whenever possible, further helps to strengthen your awareness and understanding of its incredible influence.
From these observations planetary scientists were able to determine that almost 98% of the gas in the plume is water, about 1% is hydrogen, and the rest is a combination of other molecules that include methane, ammonia, and carbon dioxide.
In September 2015, a team of astronomers released their study showing that they have detected regions on the far side of the Moon--called the lunar highlands--that may bear the scars of this ancient heavy bombardment. This vicious attack, conducted primarily by an invading army of small asteroids, smashed and shattered the lunar upper crust, leaving behind scarred regions that were as porous and fractured as they could be. The astronomers found that later impacts, crashing down onto the already heavily battered regions caused by earlier bombarding asteroids, had an opposite effect on these porous regions. Indeed, the later impacts actually sealed up the cracks and decreased porosity. | 0.842631 | 3.096519 |
Dozens of planetary nebulae are visible in a small telescope, but none present such a distinctive and accessible appearance in a small telescope as the Ring Nebula (M57) in the constellation Lyra. Seen with your eyes, the Ring Nebula will show as a tiny silver-grey smoke ring set in a rich and beautiful section of the northern summer Milky Way.
The central star of the ring, a star about the size of our own Sun, began blowing off its outer layers about 20,000 years ago, and these layers now form the nebula. Its gases are fired up by the hot stellar remnant near the center. Having lost most of its outer layers, the central star of the Ring Nebula will now become a white dwarf. This hot blue star is very faint, about magnitude 14 or 15, and only visible in 12″ or larger telescopes.
The Ring Nebula is about 2,000 light years away and spans about 0.4 light years.
A about 1/3rd of the way to top-left, you will see hint of a far away galaxy. IC 1296 is much farther away – an estimated distance of ~221-million light years as compared to M57’s mere 2000 LY.
I took this image over 395 minutes. (23 luminance of 10 minutes each and 11 images each of 5 minutes for all 3 colors). I then cropped this image by about 50% as Ring Nebula is a rather small object. | 0.808486 | 3.253536 |
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What’s more, if you look, you will find Venus shining at its maximum brightness around now as the morning star. It is always bright, but – when brightest – Venus looms as an eerie beacon in our twilight sky. It is quite a sight to see. Look eastward before dawn lights the sky.
Venus will not appear this bright in the morning sky again until July 2012. Surprisingly, Venus does not shine at its brightest when it is at full phase as seen from Earth. This world shines most brilliantly when it appears as a crescent from Earth – about one-quarter illuminated. View Venus through a telescope at morning dawn to see Venus’ crescent for yourself.
At present, Venus is waxing – increasing toward the full phase – in our morning sky. We will see Venus as full when it is far across the solar system from us, so that its fully lighted hemisphere faces our direction, by August 2011. Between now and then, as Venus waxes in phase, the planet will also be moving away from Earth – too far away, in fact, to maintain maximum brilliance. Venus’ waxing phase cannot make up for its greater distance and ever-shrinking disk. Venus greatest brilliancy depends on that critical balance between the width of Venus’ phase and Venus’ distance from Earth.
Despite Venus’ variation in brightness, this blazing world always ranks as the third-brightest celestial body, after the sun and moon.
Watch Venus continue to shine exceptionally brilliantly throughout the first week of December. After the moon drops out of the morning sky in a few more days, you may even see Venus casting a shadow before dawn – especially if your landscape is covered over by snow or white sand.
By the way, in recent years, purists have begun arguing over the differences between the terms “greatest brilliancy,” “greatest illuminated extent,” and “maximum brightness” for Venus. The distinctions between them have academic interest, but – unless you are so inclined – you can ignore the distinctions. In the actual sky, you’ll see Venus about at its brightest throughout this first week of December.
In addition, make sure to watch the coupling of the moon and Venus during the dawn and predawn hours tomorrow!
Written by Bruce McClure
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Despite suffering two glitches on its 19 October close flyby of Jupiter, NASA’s Juno spacecraft is already starting to redefine our understanding of the giant planet, scientists said at a meeting of the American Geophysical Union, on 13 December in San Francisco, California.
Better yet, two days earlier the spacecraft had completed another close flyby with no additional glitches, although mission controllers again decided not to risk using the spacecraft’s engine – which malfunctioned before the previous flyby – for a burn that would have shortened its orbit from 53 days to 14.
Also to be on the safe side, the 11 December flyby was completed with one of the spacecraft’s instruments turned off, after determining that the Jovian Infrared Aural Mapper (JIRAM) instrument was responsible for a computer reboot that had prevented the spacecraft from collecting data on the flyby in which the engine malfunctioned.
“The problem was diagnosed, but the patch has not yet been installed,” says the mission’s principal investigator, Scott Bolton.
Still, he adds, the mission has successfully collected another round of data to be added to that which it accumulated on its first close passage of the gas giant on 27 August: “We’re not exactly in the orbit we had planned [but] I can tell you that the results are pretty exciting.”
Some of these results came from the spacecraft’s microwave radiometer, which uses microwave emissions escaping from as deep as 300 to 400 kilometres beneath the cloud tops. Not only does this map the “roots” of Jupiter’s enormous cloud bands and storms, but it will determine abundances of gases such as ammonia and water.
One of this instrument’s finds, says Michael Janssen of NASA’s Jet Propulsion Laboratory in Pasadena, California, is that ammonia concentrations in Jupiter’s atmosphere vary with latitude and depth.
Of particular interest is a zone near the equator where the atmosphere is ammonia-rich all the way from the top of the atmosphere to the depths. “We have a giant plume of ammonia,” he says.
What exactly might produce such a plume is still the subject of speculation, Janssen says. In some ways, it looks like a type of circulation pattern called a Hadley cell, in which gases rise in one part of the atmosphere and descend in another.
“But if you’re pumping ammonia up, it’s got to return [to the depths] somewhere,” he says.
And so far, there’s no sign of a descending plume elsewhere.
“Welcome to the new Jupiter,” Janssen says, adding: “We have a lot of work to do.”
Other scientists have found additional intriguing results. Steve Levin, another Juno scientist from JPL, says Jupiter’s magnetic field has proved stronger and more variable from one latitude to another than expected.
Future close approaches will allow scientists to build 3-D maps not only of that field but also of Jupiter’s radiation belts, radio emissions, ionosphere and gravity field.
And of course, there are pictures. Some will be dramatic close-ups, posted via JunoCam, an instrument designed in part to let the public download images and enhance or adapt them freely.
But the spacecraft also carries four “star tracker” cameras, says Jack Connerney, of NASA Goddard Spaceflight Centre, Greenbelt, Maryland. These cameras were designed for navigation, but they can also be programmed to spot non-stellar objects.
Already they have identified dozens of such objects, Connerney says — though it is too early to specify exactly what these objects are.
Some, he says, appear to be small satellites orbiting in Jupiter’s rings. Others may be similar objects orbiting outside of the ring plane. Still others may simply be bright flashes from material blown off of Juno’s solar panels by micrometeorite impacts.
“We’re not really prepared to sort through those yet,” Connerney says. “We have to figure out if it’s a small thing close to the spacecraft or a big thing far away. It’s a big job because there’s so many of them.”
Meanwhile, the spacecraft is now moving away from Jupiter before diving in again for its next close passage on 2 February. It’s still undetermined whether it will remain on its current 53-day circuit or fire the engine to shorten its orbit.
“You might be hearing from us in little bursts every 53 days,” Levin says, “or you might start hearing from us more often.”
Richard A Lovett
Richard A. Lovett is a Portland, Oregon-based science writer and science fiction author. He is a frequent contributor to COSMOS.
Read science facts, not fiction...
There’s never been a more important time to explain the facts, cherish evidence-based knowledge and to showcase the latest scientific, technological and engineering breakthroughs. Cosmos is published by The Royal Institution of Australia, a charity dedicated to connecting people with the world of science. Financial contributions, however big or small, help us provide access to trusted science information at a time when the world needs it most. Please support us by making a donation or purchasing a subscription today. | 0.815646 | 3.623617 |
Every once in a while, we have a celestial body that passes through our solar system. What would be needed to reel one of these in? Not crashing down to Earth, that would be bad, but say into a high earth orbit (above the satellite belt)?
There have been proposals to capture a small (boulder-sized) asteroid into Earth orbit (more or less) as several other answers have discussed. This needs a lot of planning, a big rocket and a great deal of patience, but all of the asteroids being considered already orbit the Sun, and generally are among the relatively small number of asteroids that periodically come close to Earth.
Capturing an extra-solar object like Oumuamua would be much harder. Firstly we'd need to detect it a long time (decades, ideally) before it gets anywhere near the Sun, which means spotting something that is far away, very dimly illuminated, and coming from a completely unpredictable direction. We'd want to get to it as quickly as possible, break a lump off if it was too big to redirect as a whole, and then use something, probably nuclear explosives to change the course of the lump enough for it to come close to one of the giant planets, ideally Jupiter. That encounter would have to be arranged so that the planet's gravity deflects our (now slightly radioactive) lump of rock into a closed orbit around the Sun.
Once that is done, the time pressure is off, and we can use less drastic measures (rockets, light-sails,...), over possibly many decades, to steer our target lump, via whatever gravitational slingshots seem useful until it encounters the Earth and Moon at a fairly low relative velocity. Then a combination of more rockets and the Moon's gravity and maybe aero-braking in the upper atmosphere can be used (over several passes if necessary) to actually capture it.
You could look it up :-) . The basic problem is that it takes a [bleep]-load of energy to force a distant object to stop orbiting way out there and fall towards the sun, or to be exact, towards Earth. It then takes another [bleep]-load of energy to kick it back up to the needed velocity relative to Earth to be able to orbit Earth.
To some extent, you can reduce the energy required by sending it on a slow spiral, as is more or less done when sending probes to Mars, but that leads to tens of years (at best) waiting for it to arrive.
If you're thinking of comets in their extreme elliptical orbits, well, same problem, since their path is nowhere near tangent to Earth's orbit. | 0.866524 | 3.795259 |
Scientists have identified two exoplanets just 39 light years from us as potentially Earth-like following an important study by scientists at MIT. Researchers made a historic first atmospheric observation of an Earth-size planet to identify the exoplanets as being rocky, and therefore potentially habitable.
The exoplanets orbit a star called Trappist-1. It is a cold, dim red star found about 39 light years away from Earth in the constellation of Aquarius. The ultracool dwarf star is believed to be not much larger in diameter than Jupiter and is roughly 2000 times dimmer than the Sun. These types of stars make up roughly 15% of all stars in the vicinity of the Sun, and scientists believe this type of star could be the place to look for extra-terrestrial life.
Using data gathered from Hubble, researchers at MIT were able to make the first atmospheric observation of an Earth-sized planet outside of our Solar System. The observations determined that both planets lacked the atmospheric qualities to be considered a gas dwarf (effectively a mini-Jupiter), and therefore could be inferred as rocky in nature.
Although we know that these planets are rocky, the density of their atmosphere remains unknown. This information is paramount for the question of habitability to be answered, since a rocky planet like Mercury with a very thin atmosphere is clearly not habitable. However, this data may take a little while to collect. It is expected scientists will have to wait until the James Webb Space Telescope is in operation, which is still a couple of years away. With the use of the revolutionary telescope, scientists will be able to characterise the atmospheres of Earth-like planets in extraordinary, unprecedented detail. | 0.871083 | 3.448103 |
Stars light up the sky on a clear night. They may look the same from Earth, but they come in many sizes and colors. From the balanced forces of nuclear fusion and gravity keeping a star stable to their potentially violent “deaths,” explore why these huge balls of burning gas have captivated ancient and modern astronomers alike in this dynamic science e-book. Fifth-grade readers will launch into learning about the composition and classification of stars, the “life cycle” of these nonliving luminaries, galaxies, our solar system, and more through this high-interest informational text filled with vibrant photographs. Aligned to the Next Generation Science Standards, a hands-on “Think Like a Scientist” lab activity and a “Your Turn” page at the end of the e-book support STEM Education and provide young scientists with an opportunity to apply what they’ve learned in the text. Helpful diagrams, including a Venn diagram of the three types of galaxies, and text features, such as a glossary and index, are also included to reinforce content-area literacy and improve close reading.
Amidst more than 200 billion stars in a galaxy measuring 100,000 light years across, life has been discovered only in one place in the Milky Way: planet Earth. Yet the Milky Way is only one of many galaxies in the vast universe. While extraterrestrial life remains a mystery, explore discoveries about the stars and galaxies we see in the night sky with this engaging science e-book. Fifth-grade readers will launch into learning about types of galaxies, Earth’s place in the universe, properties of the Milky Way, astronomical tools, and more through this high-interest informational text filled with vibrant photographs. Aligned to the Next Generation Science Standards, a hands-on “Think Like a Scientist” lab activity and a “Your Turn” page at the end of the e-book support STEM Education and provide young scientists with an opportunity to apply what they’ve learned in the text. Helpful diagrams, a timeline of major space science discoveries from 1610 to 2010, and text features, such as a glossary and index, are also included to reinforce content-area literacy and improve close reading.
Just how big is Earth compared to our solar system, the Milky Way, or even the universe? Although Earth is home to many different species and it seems huge to us, it is very small in comparison to our solar system and the universe. Discover what scientists have uncovered so far about Earth, our solar system, and the universe in this engaging e-book. High-interest text and vibrant images and photographs fill the pages of this e-book to keep students engaged while learning about space. A “Think Like a Scientist” lab activity that supports STEM instruction is included at the end of the e-book for students to use what they learned in the text and apply that knowledge to the activity. A helpful glossary, table of contents, and index are also included for additional support.
While only 12 people have actually had contact with it, many songs and movies have featured this shining object. But it's not a superstar, or even a star at all. It's our moon. From tides and tracking time to gravitational pull on orbits, the moon affects life here on Earth. Take a trip to the moon through the fact-filled pages of this e-book! Third-grade students will enjoy learning about the physical features and phases of the moon, tides, lunar calendars, and more through this high-interest informational text filled with vibrant photographs. Aligned to the Next Generation Science Standards, a hands-on “Think Like a Scientist” lab activity is included at the end of this e-book, providing students with an opportunity to apply what they've learned in the text. Helpful diagrams, including the eight phases of the moon, and text features, such as a glossary and index, are also included to improve content-area literacy and support STEM instruction.
Learn how to create algebraic equations while traveling through our solar system! Introduce students to variables, expressions, and equations in this exciting title about the night skies. This book challenges students to learn more advanced mathematical and STEM skills, using exciting astronomy examples to keep readers engaged. Readers will practice familiar mathematical skills, like addition and subtraction, in a new way by forming equations! With eye-catching photos, easy-to-read text, and clear practice problems, this title makes mathematical concepts that could be seen as intimidating seem simple and fun instead!
Come along and explore the wonders of our solar system in this exciting title! Featuring a variety of stunning, vivid photos, helpful charts and graphs, and easy-to-read text, this book will have readers engaged from beginning to end as they learn about the sun, the eight planets in our solar system, the Milky Way Galaxy, constellations, dwarf planets, asteroids, and comets! An accessible glossary and index gives readers the tools they need while the featured lab activity provides a stimulating hands-on approach to science!
From Nicholas Copernicus to Isaac Newton, people have wondered about and studied astronomy for many years! Through vibrant images, easy-to-read text, and a hands-on lab activity, readers will be captivated as they learn about astronomers such as Galileo Galilei, Carl Sagan, and Henrietta Swan Leavitt and how their work made impacts on the field of astronomy. With a glossary and index readily available, readers will be sure to have the tools they need to better understand the content.
Come explore the wonders of space in this intriguing title that uses numerous vivid images, fascinating facts, and easy-to-read text to both delight and engage readers! From satellites to space food, observatories to Sputnik, readers will learn all about space and the various ways people have explored and learned about astronomy for years! A creative hands-on lab activity is featured to encourage children to explore astronomy even further!
Telescopes and high-tech equipment help astronomers explore deep space. This captivating title introduces readers to some of the most notable scientists who helped develop technology that allows for space exploration, such as Galileo Galilei, Edwin Hubble, Annie Cannon, George Ellery Hale, Lyman Spitzer, and Jocelyn Bell Burnell. The vibrant, stunning images and easy-to-read text will have readers engaged and eager to learn more about such topics as interstellar matter, pulsars, neutron stars, white dwarfs, and astrophysics! Readers are encouraged to explore astronomy even further with the featured lab activity!
Elementary readers will get a look into space exploration as they move through this fascinating nonfiction title. Readers will discover galaxies like the Milky Way, the effect gravity has on the inner and outer planets, comets, asteroids, constellations, and what measures scientists are taking to learn more about the vast body of the universe and more, including the Hubble Telescope and the Mars Rover. With vivid images, intriguing facts, informational text, a glossary, and a list of helpful websites, readers are encouraged to discover what they would explore in deep space!
Travel to the 22nd century in this captivating nonfiction title that allows readers to discover the future of space. Elementary readers will be fascinated with the possibilites that may await human life in the future. Readers will discover the technology that may be used to one day allow humans to live on another planet, new worlds, alien life, and artificial intelligence. Featuring vibrant photos, images, informational text, a glossary of terms, and a list of helpful websites for more explorations, children will be excited and enthralled as they move through this title.
Discover the history of the space race in this exciting and riveting nonfiction title! Elementary readers will learn about the Kennedy Space Station, the Cold War, Sputnik, the first astronauts and cosmonauts to make it into space, and the first landing on the moon. Through captivating images, informational text, and impressive facts, readers will be enthralled and inspired by the amazing accomplishments that occured during the race to space!
Readers find out what it's like for astronauts to eat, sleep, and work on a manned space flight in this adventurous nonfiction reader. Children will discover what it's like to be weightless in zero gravity, how Mission Control helps keep astronauts safe, and what astronauts do during their free time through vivid photographs, interesting, informative text, and stimulating facts.
Learn about outer space exploration, from the Hubble telescope to the latest space shuttle launches, in this delightful nonfiction title! Readers will learn about famous astronauts, the history of exploring space, and what the future holds for space exploration through vivid images and photographs, informative text, and intriguing facts. With a glossary and index, readers will want to learn all they can about exploring space!
In this encouraging nonfiction reader, children visit an actual space camp! Readers will learn what astronauts eat, where they sleep, and how they prepare for journeys into space through the help of robots and stimulators. Featuring vibrant images, informative text, and fun, interesting facts, readers are encouraged to discover what they would want to explore in space!
Readers find out what it's like for astronauts to eat, sleep, and work on a manned space flight in this adventurous nonfiction reader. Children will discover what it's like to be weightless in zero gravity, how Mission control helps keep astronauts safe, and what astronauts do during their free time through vivid photographs, interesting, informative text, and stimulating facts.
Much of what we know today about Earth is from images taken by cameras on powerful telescopes. Edwin Hubble changed our view of the universe. Working in an observatory, he found that there are other galaxies besides the Milky Way. He also showed that the universe is still growing. Lyman Spitzer, Jr. proposed placing telescopes in space, and in 1990, the Hubble Space Telescope was launched. It sends us amazing images of the universe. | 0.887937 | 3.599485 |
Astronomers from Sweden managed to find an explanation for a recent mystery in the center of the Milky Way: the high levels of scandium seen last spring near a giant black hole of the galaxy turned out to be just an optical illusion.
Last spring, researchers reported the apparent presence of surprising and dramatically high levels of three different elements in red giant stars that are 3 light years away from the central black hole. Various possible explanations were presented: the result of the destruction of early stars that fell into a black hole, or fragments from the collision of neutron stars.
The new analysis allowed us to find a more logical and simple explanation for the high levels of scandium, vanadium and yttrium. It turns out that the spectral lines presented in spring actually became an optical illusion. Spectral lines are used to find out the chemical composition of a star, focusing on its light. These giants have exhausted most of the hydrogen fuel, so the temperature reaches only half the sun.
It turns out that the lower temperature indices of stars helped to create the optical illusion that occurs when measuring spectral lines. In particular, this means that electrons in elements behave differently at different temperatures, which can also be misleading in the calculation of spectral lines in stars. A Keck telescope on Mauna Kea (Hawaii) was used for the analysis. A comprehensive mapping of the central regions of the Milky Way is under way, exploring spectral lines in the light of various stars to find out their composition. The goal is to get an idea of the events that took place in the Milky Way, and to understand the process of the birth of galaxies.
The spectral lines for each element are recorded in a high-resolution spectrometer — an advanced camera that generates a rainbow of starlight. The researchers studied part of the spectrum from near-infrared radiation - the thermal rays of stars. IR light is able to penetrate dust, interfering with the line of sight of the center of the Milky Way, which is 25,000 light-years distant. The large-scale analysis has just begun, therefore, in the near future, we are waiting for an exact result. | 0.80202 | 3.861603 |
This ghostly image shows what can happen when an interstellar cloud passes too close to a star. Barnard's Merope Nebula, also known as IC 349, is a cloud of interstellar gas and dust travelling through the Pleiades star cluster at a relative speed of 11 kilometres per second. It is passing close to the star Merope, located 0.06 light years away from the cloud, which is equivalent to about 3 500 times the distance between the Earth and the Sun. This passage is disrupting the nebula and creating the wispy effect seen in the image.
Merope is located just out of the frame at the top right. Light from the star is reflected from the surface of the cloud, which illuminates it to become what astronomers call a reflection nebula. The beams of light at the upper right from the star are an effect produced by the telescope but the eerie wisps of light from the lower left to upper right are real.
Astronomers believe that radiation pressure from the star is acting like a sieve to separate dust particles of different sizes. As the nebula approaches Merope, the starlight decelerates dust particles, but the small particles slow down more than the large particles. As an effect, the almost straight lines that are reaching out towards Merope in this view are made of large particles, whereas smaller-sized particles lag behind to create the wispy structure on the lower left.
The nebula will continue its approach towards Merope over the next few thousand years and will eventually move past the star, if it survives. Studying the nebula's interaction with the star is important as it provides a chance to observe interstellar material in an unusual situation and learn more about interstellar dust.
The nebula near Merope was discovered in 1890 by E.E. Barnard using the 36 inch telescope at the Lick Observatory in California. This image was captured by the NASA/ESA Hubble Space Telescope on 19 September 1999 and was originally published in 2000. | 0.859329 | 3.664613 |
You would think Alpha Centauri would be a prime hunting ground for extrasolar planets simply because of its proximity. But the problem for direct imaging is the sheer brightness of Centauri A and B, creating a halo of diffuse light around the pair. Getting through the glare isn’t easy, but a search based on twin techniques — adaptive optics and CCD imaging — covering a wide-field around the Centauri system has just been completed. Results on the CCD work, using European Southern Observatory equipment, have now been made available and they’ve come up short on planetary detections.
As reported by Pierre Kervella (Observatoire de Paris-Meudon) and Frederic Thévenin (Observatoire de la Côte d’Azur), the team found no co-moving companion objects between 100 and 300 AU. And that’s useful information, because it puts some constraints on possible planets around these stars. From the paper:
Within the explored area, this negative result sets an upper mass limit of 15-30 M J to the possible companions orbiting α Cen B or the pair, for separations of 50-300 AU. When combined with existing radial velocity searches…and our adaptive optics results…this mostly excludes the presence of a 20-30 M J companion within 300 AU.
First of all, note what this is not telling us. We can draw no conclusions about possible terrestrial-sized worlds orbiting within 3-4 AU of either Centauri A or B, for the equipment is not sensitive enough to detect planets that small. Thus the scenario that continues to fire the imagination of many of us — habitable planets around one or both Centauri stars — is still viable. We’ve simply learned that we can rule out massive super-Jupiters in wide orbits.
And that gives us further insight into the Alpha Centauri system itself, for some recent work has indicated that the mass of Centauri B could be higher than what earlier models have suggested. Specifically, radial velocity studies have come up with mass estimates that differ by 28 Jupiter masses (plus or minus 9) from the results of long-baseline interferometry. If the missing mass is in the form of an unseen companion, we can now exclude at least one planetary configuration that might have accounted for it.
The paper is Kervella and Thévenin, “Deep imaging survey of the environment of α Centauri,” accepted as a research note by Astronomy & Astrophysics and available as a preprint online. The team’s earlier work using adaptive optics (which feeds directly into the present paper) is Kervella et al., “Deep imaging survey of the environment of α Centauri: I. Adaptive optics imaging of α Cen B with VLT-NACO,” available here. Centauri Dreams‘ earlier story on the latter is also available. | 0.809221 | 4.024663 |
Neodymium isotope heterogeneity of ordinary and carbonaceous chondrites and the origin of non-chondritic 142Nd compositions in the Earth
Ryota Fukai, Tetsuya Yokoyama
Earth and Planetary Science Letters
Volume 474, 15 September 2017, Pages 206–214
• Ordinary and carbonaceous chondrites possess non-radiogenic Nd isotope anomalies.
• Nd isotope variability was caused by the heterogeneous distribution of s-nuclides.
• Nebular thermal processing possible cause of planetary-scale Nd isotope variability.
• Excess 142Nd of silicate Earth does not require missing enriched reservoirs.”
“We present high-precision Nd isotope compositions for ordinary and carbonaceous chondrites determined using thermal ionization mass spectrometry with dynamic and multistatic methods. The ordinary chondrites had uniform and non-terrestrial μ142Ndμ142Nd, μ148Ndμ148Nd, and μ150Ndμ150Nd values, with data that plot along the mixing line between s -process and terrestrial components in μ150Ndμ150Nd versus μ148Ndμ148Nd and μ142Ndμ142Nd versus μ148,150Nd diagrams. In contrast, the carbonaceous chondrites were characterized by larger anomalies in their μ142Ndμ142Nd, μ148Ndμ148Nd, and μ150Ndμ150Nd values compared to ordinary chondrites. Importantly, the data for carbonaceous chondrites plot along the s -process and terrestrial mixing line in a μ150Ndμ150Nd versus μ148Ndμ148Nd diagram, whereas they have systematically lower μ142Ndμ142Nd values than the s -process and terrestrial mixing line in μ142Ndμ142Nd versus μ148,150Nd diagrams. This shift likely results from the incorporation of calcium- and aluminum-rich inclusions (CAIs), indicating that the Nd isotopic variability in the ordinary chondrites and CAI-free carbonaceous chondrites was caused solely by the heterogeneous distribution of s-process nuclides. The isotopic variation most likely results from nebular thermal processing that caused selective destruction of s-process-depleted (or r-process-enriched) dust grains in the inner Solar System where the parent bodies of ordinary chondrites formed, whereas such grains were preserved in the region of carbonaceous chondrite parent body formation. The Nd isotope dichotomy between ordinary and bulk aliquots of carbonaceous chondrites can be related to the presence of Jupiter, which may have separated two isotopically distinct reservoirs that were present in the solar nebula. After correcting for s -process anomalies and CAI contributions to the Nd isotopes observed in the chondrites, we obtained a μ142Ndμ142Nd value (−2.4±4.8−2.4±4.8 ppm) that was indistinguishable from the terrestrial value. Our results corroborate the interpretation that a missing reservoir (e.g., a hidden enriched reservoir, erosional loss of crust) is not required to explain the observed differences in 142Nd/144Nd ratios between chondrites and terrestrial materials.” | 0.85625 | 3.127516 |
A “beautiful dust devil” was just discovered today, April 1, on the Red Planet by NASA’s long lived Opportunity rover as she is simultaneously exploring water altered rock outcrops at the steepest slopes ever targeted during her 13 year long expedition across the Martian surface. Opportunity is searching for minerals formed in ancient flows of water that will provide critical insight into establishing whether life ever existed on the fourth rock from the sun.
“Yes a beautiful dust devil on the floor of Endeavour Crater,” Ray Arvidson, Opportunity Deputy Principal Investigator of Washington University in St. Louis, confirmed to Universe Today. Spied from where “Opportunity is located on the southwest part of Knudsen Ridge” in Marathon Valley.
The new dust devil – a mini tornado like feature – is seen scooting across the ever fascinating Martian landscape in our new photo mosaic illustrating the steep walled terrain inside Marathon Valley and overlooking the crater floor as Opportunity makes wheel tracks at the current worksite on a crest at Knudsen Ridge. The colorized navcam camera mosaic combines raw images taken today on Sol 4332 (1 April 2016) and stitched by the imaging team of Ken Kremer and Marco Di Lorenzo.
“The dust devils have been kind to this rover,” Jim Green, Director of NASA Planetary Sciences at NASA HQ, said in an exclusive interview with Universe Today. They are associated with prior periods of solar array cleansing power boosts that contributed decisively to her longevity.
“Oppy’s best friend is on its way!”
Spotting dust devils has been relatively rare for Opportunity since landing on Mars on Jan. 24, 2004.
“There are 7 candidates, 6 of which are likely or certain,” Mark Lemmon, rover science team member from Texas A & M University, told Universe Today. “Most were seen in, on the rim of, or adjacent to Endeavour.”
Starting in late January, scientists commanded the golf cart sized Opportunity to drive up the steepest slopes ever attempted by any Mars rover in order to reach rock outcrops where she can conduct breakthrough science investigations on smectite (phyllosilicate) clay mineral bearing rocks yielding clues to Mars watery past.
“We are beginning an imaging and contact science campaign in an area where CRISM spectra show evidence for deep absorptions associated with Fe [Iron], Mg [Magnesium] smectites,” Arvidson explained.
This is especially exciting to researchers because the phyllosilicate clay mineral rocks formed under water wet, non-acidic conditions that are more conducive to the formation of Martian life forms – billions of years ago when the planet was far warmer and wetter.
“We have been in the smectite [phyllosilicate clay mineral] zone for months, ever since we entered Marathon Valley.”
The smectites were discovered via extensive, specially targeted Mars orbital measurements gathered by the CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) spectrometer on NASA’s Mars Reconnaissance Orbiter (MRO) – accomplished earlier at the direction of Arvidson.
So the ancient, weathered slopes around Marathon Valley became a top priority science destination after they were found to hold a motherlode of ‘smectite’ clay minerals based on the CRISM data.
“Marathon Valley is unlike anything we have ever seen. Looks like a mining zone!”
At this moment, the rover is driving to an alternative rock outcrop located on the southwest area of the Knudsen Ridge hilltops after trying three times to get within reach of the clay minerals by extending her instrument laden robotic arm.
Unfortunately, but not unexpectedly, the rover kept slipping on the steep walled slopes – tilted as much as 32 degrees – while repeatedly attempting close approaches to the intended target. Ultimately she came within 3 inches of the surface science target ‘Pvt. Joseph Whitehouse’ – named after a member of the Corps of Discovery.
In fact despite rotating her wheels enough to push uphill about 66 feet (20 meters) if there had been no slippage, engineers discerned from telemetry that slippage was so great that “the vehicle progressed only about 3.5 inches (9 centimeters). This was the third attempt to reach the target and came up a few inches short,” said NASA.
“The rover team reached a tough decision to skip that target and move on.”
So they backed Opportunity downhill about 27 feet (8.2 meters), then drove about 200 feet (about 60 meters) generally southwestward and uphill, toward the next target area.
NASA officials noted that “the previous record for the steepest slope ever driven by any Mars rover was accomplished while Opportunity was approaching “Burns Cliff” about nine months after the mission’s January 2004 landing on Mars.”
Marathon Valley measures about 300 yards or meters long. It cuts downhill through the west rim of Endeavour crater from west to east – the same direction in which Opportunity is currently driving downhill from a mountain summit area atop the crater rim. See our route map below showing the context of the rovers over dozen year long traverse spanning more than the 26 mile distance of a Marathon runners race.
Endeavour crater spans some 22 kilometers (14 miles) in diameter. Opportunity has been exploring Endeavour since arriving at the humongous crater in 2011.
Why are the dust devils a big deal?
Offering more than just a pretty view, the dust devils actually have been associated with springtime Martian winds that clear away the dust obscuring the robots life giving solar panels.
“Opportunity is largely in winter mode sitting on a hill side getting maximum power. But it is in a better power status than in many past winters,” Jim Green, Director of NASA Planetary Sciences at NASA HQ, told Universe Today exclusively.
“I think I know the reason. As one looks across the vistas of Mars in this mosaic Oppys best friend is on its way.”
“The dust devils have been kind to this rover. Even I have a smile on my face when I see what’s coming.”
As of today, Sol 4332, Apr. 1, 2016, Opportunity has taken over 209,200 images and traversed over 26.53 miles (42.69 kilometers) – more than a marathon.
The power output from solar array energy production has climbed to 576 watt-hours, now just past the depths of southern hemisphere Martian winter.
Meanwhile Opportunity’s younger sister rover Curiosity traverses and drills into the basal layers at the base of Mount Sharp.
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.
Learn more about NASA Mars rovers, Orion, SLS, ISS, Orbital ATK, ULA, SpaceX, Boeing, Space Taxis, NASA missions and more at Ken’s upcoming outreach events:
Apr 9/10: “NASA and the Road to Mars Human Spaceflight programs” and “Curiosity explores Mars” at NEAF (NorthEast Astronomy and Space Forum), 9 AM to 5 PM, Suffern, NY, Rockland Community College and Rockland Astronomy Club – http://rocklandastronomy.com/neaf.html
Apr 12: Hosting Dr. Jim Green, NASA, Director Planetary Science, for a Planetary sciences talk about “Ceres, Pluto and Planet X” at Princeton University; 7:30 PM, Amateur Astronomers Assoc of Princeton, Peyton Hall, Princeton, NJ – http://www.princetonastronomy.org/
Apr 17: “NASA and the Road to Mars Human Spaceflight programs”- 1:30 PM at Washington Crossing State Park, Nature Center, Titusville, NJ – http://www.state.nj.us/dep/parksandforests/parks/washcros.html | 0.863474 | 3.372493 |
Hi there! Today we will discuss on how Jupiter formed. I guess you know Jupiter, i.e. the largest planet of our Solar System. It is a gaseous planet, which means that it is composed of a large and thick atmosphere, which surrounds a solid core. Jupiter is currently studied by the NASA spacecraft Juno. The study I present you, The primordial entropy of Jupiter, by Andrew Cumming, Ravi Helled, and Julia Venturini, simulates different possible paths for the accretion of the atmosphere of Jupiter. The goal is to compare the outcomes with the current atmosphere, to eventually discard some scenarios and constrain the primordial Jupiter. This study has recently been published in The Monthly Notices of the Royal Astronomical Society.
The planet Jupiter
Jupiter is the largest planet of our Solar System, and the most massive one. It is about 1,000 more massive than our Earth, and 1,000 less massive than the Sun. As such, it has a tremendous influence on the architecture of our System, particularly the small bodies. The Main Asteroid Belt presents gaps, which are due to mean-motion resonances with Jupiter. Jupiter is also responsible for the destabilization of the orbits of objects which pass close to it. A famous example is the comet Shoemaker-Levy 9 which Jupiter tidally destroyed before its impact. You can find below a comparison between Jupiter, Saturn, and our Earth.
|Equatorial radius||71,492 km||60,268 km||6,378 km|
|Polar radius||66,854 km||54,364 km||6,357 km|
|Distance to the Sun||5.20 AU||9.58 AU||1 AU|
|Orbital period||11.86 yr||29.46 yr||1 yr|
|Spin period||9 h 55 m||10 h 33 m||23 h 56 m|
|Density||1.326 g/cm3||0.687 g/cm3||5.514 g/cm3|
I compare with our Earth given our special connection with that planet, but the comparison with Saturn is much more relevant from a physical point of view. For gaseous planets, the radius correspond to an atmospheric pressure of 1 bar. I here provide a unique spin period, but the gaseous planets experience differential rotation, i.e. the equator may spin slightly faster than the poles.
You can see that our Earth is much denser than the giant guys. The reason is the thick atmosphere, which is less dense than a rocky body. Actually Jupiter is assumed to have a rocky core as well, which would be surrounded by hydrogen, which pressure increases with the depth.
Observers especially know Jupiter for its Great Red Spot, i.e. a giant storm, which is observed since the 17th century.
Jupiter is currently the target of the NASA mission Juno.
The mission Juno
The NASA mission Juno has been sent from Cape Canaveral in August 2011, and orbits Jupiter since July 2016, on a polar orbit. The nominal mission will be completed in July 2018, but I hope it will be extended (I do not have information on this point, sorry). Its goals are to understand origin and evolution of Jupiter, look for solid planetary core, map magnetic field, measure water and ammonia in deep atmosphere, observe auroras.
It is composed of 9 instruments. Beside impressive images of cyclones in the atmosphere of Jupiter, it for instance gave us its gravity field of Jupiter with an unprecedented accuracy. Such a result permits to constrain the interior, see for instance this study, in which the authors modeled different interiors for Jupiter. They then compared the resulting, theoretical gravity field, which the one actually measured by Juno. They deduced that the core contains between 7 and 25 Earth masses of heavy elements.
The study I present today does not model the present Jupiter, but instead simulates the evolution of Jupiter from its early life to present. Once more, the goal is to compare with current and future observations. Let us see how a giant planet evolves.
The formation of a giant planet
There are two identified scenarios for the triggering of the formation of a planet:
- Disk instability: a massive disk fragments into planet-sized self-gravitating clumps
- Core accretion: solid particles collide and coagulate into larger and larger bodies until a body large enough to accrete a gaseous envelope.
The core accretion model consists of 3 phases:
- Primary core/heavy-element accretion: here you create the solid core,
- Slow envelope/gas accretion: in this phase, the solid core continues growing, while gas accretes as well,
- Rapid gas accretion: this is the final stage, where the core has already been formed.
Here the authors simulate the Phase 3. They are particularly interested in the heat transfer inside the atmosphere. There are two ways to transport heat in such an environment: by radiation, or by convection, i.e. transport of gas, which is a much more effective process. Moreover, convection permits the transport of heavy elements, and so a gradient of density in the atmosphere. This gradient of density would eventually stop the convection, the atmosphere reaching a kind of equilibrium.
Let us see how the authors simulated that process.
Simulations of different scenarios
The authors simulated the gas accretion of Jupiter using the numerical MESA code, for Modules for Experiments in Stellar Astrophysics. Yes, stellar, not planetary. But this is very relevant here, since a gaseous planet and a star are both made of a thick gaseous envelope.
These simulations differ by
- The initial mass of the core,
- its initial luminosity, which affects the heat transfers during the accretion process. This could be expressed in terms of entropy, which is a thermodynamical quantity expressing the overall activity of a fluid. It will then express the quantity of conductive transfers,
- the initial mass of the envelope,
- the temperature of the accreted material,
- the time-dependent accretion rate. In some simulations it is an ad-hoc model, fitted from previous studies, and in other ones it is directly derived from formation models. The accretion rate is obviously time-dependent, since it slows down at the end of the accretion,
- the opacity of the material, which is defined as the ratio of the gravitational acceleration over the pressure, multiplied by the optical depth. This affects the heat transfers.
And from all of these simulations, the authors deduce some properties of the final Jupiter, to be compared with future observations to constrain the evolution models.
The initial state constrains the final one
And here are some of the results:
- Lower opacity and lower solid accretion rate lead to a low mass core,
- if the gas accretion rate is high then the proto-Jupiter is likely to be fully radiative, i.e. no convection,
- the rate at which the accretion slows down at the end determines the depth of the convection zone,
At this time, we do not dispose of enough data to constrain the initial parameters and the accretion rates, but why not in the future? Juno is still on-going, and we hope other missions will follow. For instance, stable regions in Jupiter’s interior can be probed with seismology. Seismology of giant planets would be pretty similar to helioseismology, i.e. this would consist in the detection of acoustic waves, which would be generated by convection in the interior.
The study and its authors
- You can find the study here. The authors made it freely available on arXiv, thanks to them for sharing! And now the authors:
- The website of Andrew Cumming, first author of the study,
- and the one of Ravit Helled. | 0.933546 | 3.705564 |
Equinox & Solstice4.12 - Understand the astronomical significance of equinoxes and solstices
4.13 - Understand the variation in the Sun’s apparent motion during the year, particularly at the equinoxes and solstices
Above the Equator is the Northern Hemisphere; below it is the Southern Hemisphere. Imagine if the Equator is projected into space. This would be called the celestial equator.
The path the Sun appears to take over the course of a year is called the ecliptic. This is the path of the Earth's orbit.
The Earth's axis is titled at an angle of 23.5 (22.26)° to the ecliptic.
Every day the Sun appears to move 1 degree eastwards. This is because there are 360° in a circle and 365 days in a year.
Between December and June, the Sun is in position above the celestial equator and the Northern Hemisphere receives more daylight. Between June and December, the Sun is below the celestial equator and the Southern Hemisphere receives less daylight.
During the summer months in the Northern Hemisphere the North Pole receives sunlight for 6 months and the Sun does not set. During the winter there is darkness for 6 months. The opposite is happening at the South Pole in this time.
Let's look at some 'lines' to understand this. The equator is an imaginary line around the widest point of the Earth.
There are two other lines of latitude which we need to learn. These are the Tropics of Capricorn and Cancer. They are named after these constellations as they are named after the constellation the Sun is in at different parts of the day.
Around 21st March and 21st September the Sun passes over the celestial equator. If you were standing on the Equator the Sun would be directly above your head at midday. These dates are called the equinox, when day and night are of equal length around at every point on Earth.
Around 21st December the Sun is at its furthest point southwards on the Ecliptic. If you were standing on the Tropic of Capricorn, you would see the Sun above you at midday.
Around 21st June the Sun is at its furthest point northwards on the Ecliptic. If you were standing on the Tropic of Cancer you would see the Sun above you at midday.
These dates are called the Solstice; when day is at its shortest or longest.
The equinox does not stay at the same time every year. Earth's axis wobbles slightly like a spinning top. This means that the Vernal Equinox is getting slightly earlier each year. This is called "Precession of the Equinoxes". The point at which the Sun crosses the ecliptic at the Vernal Equinox is called the "First point of Aries" and since our ancients observed it in Aries, it has shifted into the constellation of Pisces and in the not distant future will occur in Aquarius.
Mix & Match
- Explain why Earth has seasons
- Describe the terms 'Equinox' and 'Solstice'
Did you know?
At the poles during the winter there is darkness for 6 months. Although the Sun is below the horizon during this time, there is civil twilight when the sun is up to 6 degrees below the horizon. At the North Pole this occurs for a fortnight. Nautical twilight when the sun is between 6 and 12 degrees below the horizon occurs until the mid-November when astronomical twilight (what we call nighttime) continues until the end of January.
Approx. Equinox and Solstice Dates
NH = Northern Hemisphere
SH = Southern Hemisphere
- Zoom Astronomy Seasons & Tilt
- Bad Astronomy About the seasons
- Harvard-Smithsonian Center for Astrophysics High Energy Astrophysics Division Activities about Earth's orbit/seasons etc
- Bad Astronomy When Seasons Start
- Time and Date Equinoxes, Solstices | 0.879426 | 3.586515 |
Ever since Pluto got voted off the island, most astronomers have defined a planet as a body orbiting a star—dead or alive—that is a) massive enough to be rounded by its own gravity, b) not massive enough to ignite itself into starhood, and c) domineering enough to have swept its neighborhood clean of smaller planetary seedlings.
Phew, what a mouthful!
But as we know from our own solar system, not all planets are created equal, and things get really interesting when we try to define the types of planets that might support life.
Traditionally when we think of a habitable world, we think of Earth. Makes sense: To date it’s our only frame of reference for a planet that supports plants, animals, even microbes. So it’s as good a model as any in terms of what we’d want habitable exoplanets to look like.
A 3-D view of Mount Kilimanjaro in Tanzania, compiled from satellite data
—Image courtesy NASA/JPL/NIMA
Hence the huge emphasis among planet hunters on the so-called Goldilocks Zone, where it’s not too hot and not too cold. A planet inside this zone would be just right for liquid water and life-giving sunshine.
In recent years that hypothetical zone has been getting bigger, it seems, especially as expeditions to the deep ocean and volcanic peaks have expanded the conditions in which we thought life could exist.
Enter Rory Barnes, a University of Washington postdoctoral researcher who’s here to rain on that parade.
In addition to the right amounts of heat and water, planets that could support life need just the right kind of plate tectonics, Barnes argues in a paper soon to appear in the Astrophysical Journal Letters.
Plate tectonics on Earth plays a role in climate, Barnes says, by contributing to the global carbon cycle that keeps the atmospheric greenhouse effect well balanced [human emissions excluded, of course].
“If you have plate tectonics, then you can have long-term climate stability, which we think is a prerequisite for life,” Barnes said in a statement.
No tectonics and you get a dead world, a la Mars.
On the other hand, too much tectonics and a planet’s surface gets reshuffled too fast and furious. It’d be like a dandelion trying to grow in a crack on a well-maintained freeway—things would get repaved too quickly for life to keep its grip.
Take Jupiter’s moon Io, for example. Although far from the sun, the moon is jostled between Jupiter and two larger moons, which creates what’s known as tidal heating—heat from friction as the intense and irregular pull of gravity moves the moon’s crust.
—Image courtesy NASA/JPL/University of Arizona
All this motion makes Io volcanically active, but so very active that scientists don’t think the moon is a candidate for life.
Barnes therefore proposes establishing a “tidal habitable zone,” where a planet is close enough to its star for stellar gravity to drive plate tectonics, but not so close that tectonics goes on overdrive and the surface is constantly changing.
This, apparently, would squelsh fans of Gliese 581d, an exoplanet championed by some as the most likely “other Earth” yet found.
Recent calculations placed the rocky world within its star’s habitable zone. But Barnes’ theory says poor Gliese would be outside the zone for ideal tidal forces.
“Overall, the effect of this work is to reduce the number of habitable environments in the universe, or at least what we have thought of as habitable environments,” Barnes said.
“The best places to look for habitability are where this new definition and the old definition overlap.” | 0.876855 | 3.619411 |
Find a place far away from city lights to lean back and marvel at the night sky.
Millions of stars shining bright, so far away you can’t even comprehend the distance, yet they’re all in our very own galaxy.
As your eyes adjust to the darkness you’ll start seeing more and more stars.
Moving through time and space wondering what your purpose really is in the grand scheme of things.
The mountain tops you see in the distance, huge compared to us but dwarfed against the backdrop of the vastness of space.
You notice a small, blurry spot of light, different from all the other stars and planets you can see.
Like a tiny little cloud but it’s glowing.
You’re gazing at a whole other world.
Far, far away from all the stars you can see, 2,5 million light-years away from our entire galaxy.
You’re seeing it as it looked 2,5 million years ago, that’s how long it’s light has been travelling to greet your eyes at this very moment.
If we were to travel at light speed it would take us 2,5 million years to reach it.
Our galaxy, the Milky Way, and the Andromeda Galaxy are actually being pulled closer to each other, at 402,000 kilometers per hour.
4 billion years from now they will finally collide and eventually merge into a new galaxy. “Eventually” in this scenario meaning billions of years from now.
That’s as far as we can see with the naked eye, in binoculars or through a telescope the view is spellbinding.
Dark sky spots are sadly becoming few and far between but if you manage to find one, far away from light pollution, let your eyes adjust to the darkness. Avoid looking at phone screens or using flashlights, just sit for a while looking at the sky.
As your eyes become accustomed to the darkness you’ll see more and more stars appear. After a while you’ll find it hard to make out the most well known constellations because there are just too many stars.
You notice something strange, a glowing band stretching across the sky. Brighter than the starfilled sky around it, like a gas cloud had been sprayed from horizon to horizon. As you keep watching you see that you’re looking at a band of layers upon layers of stars, our street in the universe, our galaxy from within.
You might start noticing little clusters of stars, like fuzzy balls of light, globular clusters like the Beehive or Double Cluster.
Or open clusters like the famous Pleiades, the Seven Sisters with visible nebulosity.
If you focus your attention just south of Orion’s Belt in the constellation of Orion you’ll see another fuzzy “cloud”, the Orion Nebula. You are watching a stellar nursery, a place where stars are being born.
To the naked eye it looks like a gray hazy spot, like a tiny cloud with edges you can’t quite make out.
I remember the first time I saw the Orion Nebula, or M42, through a small telescope, it almost moved me to tears.
When I took a picture of it and saw the colors the sensor in my camera captured, I was blown away.
Much closer than that we find our brightest stars, apart from the sun of course.
Sirius, the brightest one, only 8,6 light years away, is visible low down in the winter sky up here.
I say “one” but Sirius is actually a binary star, consisting of two stars but they look like one to us.
And then there’s our home in this galaxy, our corner of the Milky Way: the Solar System.
We can easily see Mercury, Venus, Mars, Jupiter and Saturn with our unaided eyes and Uranus and Neptune through binoculars or telescopes. (Uranus can be seen with the naked eye if your eyes are sharp!)
And then there’s the aurora.
That beautiful cosmic dancer, the mind blowing light show in the sky.
What a beautiful reminder of our magnetic field, always there to protect us.
Apart from all those objects we’ll also see an array of satellites on any given night, not to mention the International Space Station! Sadly we can’t see the ISS from up here but you probably can where you are.
If you’re lucky you might also see some meteors whizzing by, creating a spectacular show as they burn in our atmosphere.
If you’re incredibly lucky, and/or very dedicated, you might even find a meteorite. A piece of debris which has travelled from outer space and survived the harsh journey through our atmosphere before landing here on Earth.
Once part of an asteroid or a comet or maybe a meteoroid, now resting in your human hands.
Wouldn’t that be something? | 0.87835 | 3.514185 |
Researchers working with data from NASA’s TESS (Transiting Exoplanet Survey Satellite) have a found a planet that orbits two stars. Initially, the system was identified by citizen scientists as a pair of eclipsing binary stars without a planet. But an intern taking a closer look at that data found that it was misidentified.Continue reading “TESS Finds a Planet That Orbits Two Stars”
A quiet milestone in modern astronomy may soon come to pass. As of today, The Extrasolar Planets Encyclopedia lists a current tally of 998 extrasolar planets across 759 planetary systems. And although various tabulations differ slightly, very soon we should be living in an era where over one thousand exoplanets are known.
The history of exoplanet discovery has paralleled the course of the modern age of astronomy. It’s strange to think that a generation has already grown up over the past two decades in a world where knowledge of extrasolar planets is a given. I remember hearing of the promise of such detections growing up in the 1970’s, as astronomers put the odds at detection of planets beyond our solar system in our lifetime at around 50%.
Sure, there were plenty of false positives long before the first true discovery was made. 70 Ophiuchi was the site of many claims, starting with that of W.S. Jacob of the Madras Observatory way back in 1855. The high proper motion exhibited by Barnard’s Star at six light years distant was also highly scrutinized throughout the 20th century for claims of an unseen companion causing it to wobble. Ironically, Barnard’s Star still hasn’t made it into the pantheon of stars boasting planetary worlds.
But the first verified claim of an exoplanetary system came from a bizarre and unexpected source: a pulsar known as PSR B1257+12, which was discovered to host two worlds in 1992. This was followed by the first discovery of a world orbiting a main sequence star, 51 Pegasi in 1994. I still remember getting my hands on the latest issue of Astronomy magazine— we got our news, often months later, from actual paper magazines in those days —announcing “Planet Discovered!” on the cover.
Most methods and techniques used to discover exoplanets rely on either radial velocity or dips in the light output of a star from a transiting world. Both have their utility and drawbacks. Radial velocity looks for shifts in the star’s spectra as an unseen companion tugs it around a common center of mass. Though effective, it can only place a lower limit on the planet’s mass… and it’s biased towards worlds in short orbits. This is one reason that “hot Jupiters” have dominated the early exoplanet catalog: we hadn’t been looking for all that long.
Another method famously employed by surveys such as the Kepler space telescope is the transit detection method. This allows a much more refined estimate of a planet’s mass and orbit, assuming it transits the disk of its host star as seen from our Earthly vantage point in the first place, which most don’t.
Direct detection via occulting the host star is also coming of age. One of the first exoplanets directly imaged was Fomalhaut b, which can be seen changing positions in its orbit from 2004 to 2006.
Gravitational microlensing has also bared planetary fruit, with surveys such as MOA (Microlensing Observations in Astrophysics) and OGLE (the Optical Gravitational Lensing Experiment) catching brief lensing events as an unseen body passes in front of a background star. Distant free-ranging rogue planets can only be detected via this method.
More exotic techniques also exist, such as relativistic beaming (sounding like something out of Star Trek). Other methods include searches for tiny light variations as an illuminated planet orbits its host star, deformities caused by ellipsoidal variations as massive planets orbit a star, and infrared detections of circumstellar disks. We’re always amazed at the wealth of data that can be teased out of a few dim photons of light.
Universe Today has grown up with exoplanet science, from reporting on the hottest, fastest, and other notable “firsts”. A bizarre menagerie of worlds are now known, many of which defy the imagination of science fiction writers of yore. Want a world made of diamond, or one where it rains glass? There’s now an “exoplanet for that”.
Exoplanet surveys also have a capacity to peg down that key fp factor in the famous Drake equation, which asks us “what fraction of stars have planets”. It’s been long suspected that stars with planets are the rule rather than the exception, and we’re just now getting hard data to back that assertion up.
Missions, such as NASA’s Kepler space telescope and CNES/ESA CoRoT space telescope have swollen the ranks of extrasolar worlds. Kepler recently ended its career staring off in the direction of the constellations Cygnus, Hercules and Lyra and still has over 3,200 detections awaiting confirmation.
But is a given world Earthlike, or just Earth-sized? That’s the Holy Grail of modern exoplanet detection: an Earth-sized world orbiting in a star’s habitable zone. We’re cautious every time the latest “Earth-twin” makes its way into the headlines. From the perspective of an intergalactic astronomer, Venus in our own solar system might appear to fit the bill, though I wouldn’t bank the construction of an interstellar ark on it and head there just yet.
Exoplanet science has definitely come of age, allowing us to finally begin characterization of solar systems and give us some insight into solar system formation.
But perhaps what will be the most enduring legacy is what the discovery of extrasolar planets tells us about ourselves. How common (or rare) is the Earth? How typical is the story of our solar system? If the “first 1,000” are any indication, we strongly suspect that terrestrial planets come in enough distinct varieties or ”flavors” to make Baskin Robbins envious.
And the future of exoplanet science looks bright indeed. One proposed mission, known as the Fast INfrared Exoplanet Spectroscopy Survey Explorer, or FINESSE, would target exoplanet atmospheres, if given the go ahead for a 2017 launch. Another proposal, known as the Wide Field Infrared Survey Telescope, or WFIRST, would search for microlensing events starting in 2023. A mission that scientists would love to fly that always seems to be shelved is known as the Terrestrial Planet Finder.
But the exoplanet hunting mission that’s closest to launch is the Transiting Exoplanet Survey Satellite, or TESS. Unlike Kepler, which stares at a single patch of sky, TESS will be an all-sky survey looking at a half million stars.
We’re also just approaching an era where spectroscopy may allow us to detect exomoons and the chemistry taking place on these far off exoworlds. An example of an exciting discovery would be the detection of a chemical such as chlorophyll, a chemical that we know on Earth only exists as the result of life. But what a tantalizing discovery a blip on a graph would be, when what we humans really want to see is the vista of those far-flung alien forests!
Such is the exciting era we live in. Congratulations, humanity, on detecting 1,000 exoplanets… here’s to a thousand more! | 0.918143 | 3.749851 |
One can only speculate on the cosmic mysteries of the universe—and humans have spent millennia doing just that.
September’s full Moon is coming up, the so-called “Harvest Moon,” which is the full Moon nearest to the autumnal equinox (Sept. 23).
According to the Farmers’ Almanac, arrival of this year’s Harvest Moon will depend on which time zone you happen to live in. For those of us in the Eastern Time Zone, the moment the Moon turns full will occur just after midnight—at 12:33 a.m. on Saturday, the 14th. But if you live elsewhere in the country—in the Central, Mountain, or Pacific time zones—the moment that the Moon turns full comes before midnight on Friday, the 13th!
Interestingly, the last time this happened—June 13, 2014—it was the reverse of what will happen this month. It was a Friday, the 13th full Moon solely for the Eastern Time Zone, with the Moon turning full just after midnight; for the rest of the country, the full Moon was the day before, on Thursday, the 12th. Nationwide, we haven’t had a Friday the 13th full Moon since Oct. 13, 2000, and it won’t happen again until Aug. 13th, 2049!
It has been calculated that to have a full Moon occur on the 13th day of a particular month, and for that day to be a Friday, it is (on average) a once in 20-year occurrence.
Farmers' Almanac reports that what sets this upcoming full Moon apart from the others is that farmers, at the peak of the current harvest season, can work late into the night by this Moon’s light. The Moon rises about the time the sun sets, but more importantly, at this time of year, instead of rising its normal average 50 minutes later each day, the Moon seems to rise at nearly the same time each night leading up to when it’s full.
For example, between Sept. 12 and 14, the rising of the Moon comes, on average, less than 27 minutes later each night, thus providing light for the farmer to continue gathering crops, even after the sun has set.
The reason for this seasonal circumstance is that at this time of the year, the path of the Moon through the sky is as close to being along the horizon as it can get. Thus, from night to night the Moon moves more horizontally than vertically and so rises sooner from one night to the next.
To add to this full Moon “madness,” this upcoming full Moon very nearly coincides with apogee—that point in its orbit which places it at its greatest distance from the Earth: 252,100 miles away. Last February, the full Moon coincided with perigee, its closest point to Earth. The Moon was more than 30,000 miles closer and was accordingly branded a “Supermoon.”
According to reports, this month’s full Moon will appear about 14 percent smaller, leading some to call it a “Micro” Moon. Many will claim that this year’s full Harvest Moon indeed appears to be smaller than usual. But without knowing in advance whether a full Moon of a given month might be branded either “Super” or “Micro,” the appearance of our natural satellite to most really won’t look all that much different.
No matter its size, since I was a child, I've remained moonstruck by its beauty. Whenever there's an eclipse or some type of event about the Moon, I usually have my eyes skyward.
Luckily, my husband is just about as looney as I am about terrestrial happenings. We've been known to sit at the local airport in our lawn chairs to view whatever is projected to happen.
Here’s hoping for clear skies so anyone else who's looney about the moon can get outside and enjoy it. And whether or not it happens on Friday the 13th, it's mysteries still intrigue!
Nancy Hastings is a Daily News staff writer and can be reached at [email protected]. Follow her on Twitter: @nhastingsHDN. | 0.863714 | 3.311668 |
Using the new extreme-AO instrument SPHERE, researchers image the prototype eclipsing post-common envelope binary V471 Tau in search of the brown dwarf that is believed to be responsible for variations in its eclipse arrival times.
The new SPHERE instrument on ESO’s Very Large Telescope has been used to search for a brown dwarf expected to be orbiting the unusual double star V471 Tauri. SPHERE has given astronomers the best look so far at the surroundings of this intriguing object and they found — nothing. The surprising absence of this confidently predicted brown dwarf means that the conventional explanation for the odd behavior of V471 Tauri is wrong. This unexpected result is described in the first science paper based on observations from SPHERE.
Some pairs of stars consist of two normal stars with slightly different masses. When the star of slightly higher mass ages and expands to become a red giant, material is transferred to other star and ends up surrounding both stars in a huge gaseous envelope. When this cloud disperses the two move closer together and form a very tight pair with one white dwarf, and one more normal star .
One such stellar pair is called V471 Tauri . It is a member of the Hyades star cluster in the constellation of Taurus and is estimated to be around 600 million years old and about 163 light-years from Earth. The two stars are very close and orbit each other every 12 hours. Twice per orbit one star passes in front of the other — which leads to regular changes in the brightness of the pair observed from Earth as they eclipse each other.
A team of astronomers led by Adam Hardy (Universidad Valparaíso, Valparaíso, Chile) first used the ULTRACAM system on ESO’s New Technology Telescope to measure these brightness changes very precisely. The times of the eclipses were measured with an accuracy of better than two seconds — a big improvement on earlier measurements.
The eclipse timings were not regular, but could be explained well by assuming that there was a brown dwarf orbiting both stars whose gravitational pull was disturbing the orbits of the stars. They also found hints that there might be a second small companion object.
Up to now however, it has been impossible to actually image a faint brown dwarf so close to much brighter stars. But the power of the newly installed SPHERE instrument on ESO’s Very Large Telescope allowed the team to look for the first time exactly where the brown dwarf companion was expected to be. But they saw nothing, even though the very high quality images from SPHERE should have easily revealed it .
“There are many papers suggesting the existence of such circumbinary objects, but the results here provide damaging evidence against this hypothesis,” remarks Adam Hardy.
If there is no orbiting object then what is causing the odd changes to the orbit of the binary? Several theories have been proposed, and, while some of these have already been ruled out, it is possible that the effects are caused by magnetic field variations in the larger of the two stars , somewhat similar to the smaller changes seen in the Sun.
“A study such as this has been necessary for many years, but has only become possible with the advent of powerful new instruments such as SPHERE. This is how science works: observations with new technology can either confirm, or as in this case disprove, earlier ideas. This is an excellent way to start the observational life of this amazing instrument,” concludes Adam Hardy.
Such pairs are known as post-common-envelope binaries.
This name means that the object is the 471st variable star (or as closer analysis shows, pair of stars) to be identified in the constellation of Taurus.
The SPHERE images are so accurate that they would have been able to reveal a companion such as a brown dwarf that is 70 000 times fainter than the central star, and only 0.26 arcseconds away from it. The expected brown dwarf companion in this case was predicted to be much brighter.
This effect is called the Applegate mechanism and results in regular changes in the shape of the star, which can lead to changes in the apparent brightness of the double star seen from Earth.
Publication: A. Hardy, et al., “The First Science Results from Sphere: Disproving the Predicted Brown Dwarf Around V471 Tau,” 2015, ApJ, 800, L24; doi:10.1088/2041-8205/800/2/L24
Images: ESO/J. Girard; ESO/Digitized Sky Survey 2 | 0.897786 | 3.990727 |
Researchers, for the first time, have noticed something unique in the sky. They have observed the birth of the planet.
Have you ever wondered- how do scientists and researchers work in detail in proving a particular theory or occurrence? Sometimes it takes over 30 years of research to come to a final point.
Recent research at the European Southern Observatory’s Very Large Telescope in Chile captured the birth of the planet for the first time. The picture shows the thick layer of dust and gas around a young star named AB Aurigae.
It also shows the rose-like spirals that are the sign of the birth of the baby planet. It indicates how the young objects disrupt the gas and cause waves as if it were a boat on a lake.
The yellow region near the spiral center is at the same distance from the star as Neptune is from the sun.
The study co-author, Anne Dutrey of the Astrophysics Laboratory of Bordeaux (LAB) in France, explained-
"The twist is expected from some theoretical models of planet formation."
“It corresponds to the connection of two spirals—one winding inwards of the planet's orbit, the other expanding outwards—which join at the planet location.”
According to NASA, planets form from grains of dust smaller than the width of a human hair, emerging from expansive, donut-shaped disks of dust and gas usually float around young stars. Gravity and other forces fuse the materials, and then they accumulate and grow like snowballs. The snowballs are transformed into pebbles and then into mile-wide rocks. Years later, you would have a small planet on your hands.
The image captured is the deepest photograph ever taken of the AB Aurigae. Observation of this constellation was made a few years ago, with the Atacama Large Millimeter/submillimeter Array (ALMA). This year, Anthony Boccaletti and a team of astronomers from Taiwan, France, the United States, and Belgium collaborated to click the image of the area by turning the VLT in Chile toward the young star.
European Southern Observatory is amid constructing the Extremely Large Telescope with a 39-meter-wide main mirror. It is the largest of its kind and would provide an intimate glimpse into deep space. By the end of 2025, the new instrument would show dust grains and other small materials from planet bearing discs, which would make clear how planets are born.
"We should be able to see directly and more precisely how the dynamics of the gas contributes to the formation of planets."
"I can't really face small, irregularly or asymmetrically placed holes, they make me like, throw up in my mouth, cry a little bi...
A lefty or left-handed uses his left hand more naturally and dominantly than the right hand. And the righty or right-handed is o...
Watching celestial objects is a true delight. It is still fun to catch a sight of shooting stars when we grow up. A second of th... | 0.853744 | 3.859078 |
For nearly 20 years, NASA has been planning and constructing a telescope unlike any ever built before: the James Webb Space Telescope. It will change the way scientists see the most distant galaxies and intensify the hunt for extraterrestrial life; it will answer outstanding questions about the birth and death of stars and planets. It is the future of astronomy—but it’s causing trouble. JWST’s high price and decade of delays could stymie the development of future telescopes, impacting the course of astronomy for the next 30 years.
Billed as a successor to the Hubble Space Telescope, the JWST is a tennis court-sized, general-purpose space telescope with a 6.5-meter mirror that will be sent to a gravitationally stable point nearly a million miles from Earth. It will create incredibly detailed images from the infrared light of objects in space, including nebulae, exoplanets, galaxies, and stars. Looking even further ahead, NASA’s planned successor to JWST, called the Wide Field Infrared Survey Telescope (WFIRST), will observe the sky with resolution similar to Hubble’s but with a far wider field of view. That would allow astronomers to answer some of the fundamental questions about dark energy, a mysterious force that seems to be driving the universe’s accelerating expansion. It would also provide a platform to test state-of-the-art components for its own successor. Four teams of scientists are already working on different concepts for the flagship mission to follow WFIRST, which would launch in the 2030s or 2040s. Three of those concepts would follow up on potentially life-harboring exoplanets spotted by JWST, while the fourth would aim to understand the origins of galaxies and the universe itself. These missions would all be expensive, similar in cost to JWST.
“[Today’s astronomers] are the first humans in history that have a chance to answer the compelling questions about whether there is life beyond Earth,” MIT astrophysicist Sara Seager recently told the Senate.
But as the JWST’s price tag has increased incrementally, from hundreds of millions of dollars to $US9.6 ($14) billion, some scientists working on its successors are uneasy. Where does the extra money come from to pay for JWST’s budget overruns, and how have these delays affected public perception of these large missions? And if NASA scraps or removes certain parts from WFIRST, that might handicap future space-based efforts to detect signs of life outside the Solar System. While Congress views astronomy research more favourably, President Trump’s 2019 budget request has already suggested scrapping WFIRST.
As of now, the future of these missions and how JWST will impact them is uncertain, Scott Gaudi, Ohio State University professor and member of the WFIRST team, told Gizmodo.
As early as 1989, astronomers had an early concept of JWST as a “Next Generation Space Telescope,” the successor to Hubble. While originally envisioned as having a mirror eight or more meters (26+ feet) in diameter, budget constraints caused scientists to de-scope various goals, resulting in the 6.5-meter (21-foot) telescope concept that would become the James Webb Space Telescope. As plans developed, NASA in 2002 selected an aerospace company called TRW to build the spaceship and mirror with an $US825 ($1,164) million budget and a scheduled launch in 2010. Northrop Grumman acquired TRW, and soon took over the telescope’s construction.
Delays have marred JWST’s entire developmental history. Most recently, an independent review revealed that increase in project scope, the complexity of the telescope, overoptimism, and human errors have plagued its construction. Those human errors include the time when someone at Northrop Grumman used the wrong solvent to clean valves, and the time when loose nuts fell into the telescope during a test, according to the review. But as early as 2005, the launch had been pushed to 2013 and the cost to $US4.5 ($6) billion due to “funding shortfalls,” “requirement changes,” and other issues. Fabrication began in 2011, but by then the launch was pushed to 2018 and the budget to an estimated $US8 ($11) billion. Today, the JWST’s estimated cost is up to $US9.66 ($14) billion, and its projected launch date is some time in 2021.
Then there’s the mere fact that huge advances in astronomy have occurred during the telescope’s development. NASA administrator Jim Bridenstine explained in a Congressional hearing this past July that the study of today’s most ubiquitous astronomy topics, like dark energy and exoplanets, was only beginning when the JWST project began. “This isn’t simply mismanagement or cost overruns or delay,” Congressman Don Beyer (D-Virginia) said during the hearing. “The world of science itself is changing in ways that have impacted the project.” Essentially, the price and scope of the project have expanded as scientists have learned more about the universe and encountered more cosmic mysteries.
By 2010, it was already time to plan a successor for JWST. Every decade, committees of scientists survey the state of astrophysics and decide what kind of experiments the entire community would like to see next, including small- and medium-sized missions as well as the flagship missions. For the largest missions, teams of scientists work on multiple concepts, and the Decadal Survey committee uses these concepts to set the field’s priority for NASA.
Even back then, astronomers worried about how JWST’s cost would affect the future of observation. But then NASA received a 2.4-meter mirror from National Reconnaissance Office (NRO). The mirror was initially designed for use in espionage, but would work nicely in a space telescope. The Decadal Survey moved forward with a telescope called WFIRST—a telescope with Hubble’s resolution but 100 times the viewing area. A telescope like this would help scientists determine the true nature of dark energy, a mysterious force that seems to be speeding up the universe’s expansion and that could determine the universe’s ultimate fate. NASA scrapped other concepts, like the exoplanet-hunting Space Interferometry Mission, in response.
WFIRST “was a Frankenstein creation,” Jessie Christiansen, astrophysicist at the NASA Exoplanet Science Institute at Caltech, told Gizmodo. “It was something no one really asked for until they got the mirror donated by the NRO.” But, according to the Decadal Survey, such a telescope would “settle essential questions in both exoplanet and dark energy research, which will advance topics ranging from galaxy evolution to the study of objects within our own galaxy.” WFIRST has expanded in both scope and cost since the 2010 decadal survey.
The telescope’s wide-field surveying instrument would be relatively simple compared to some instruments flown on previous NASA missions, Gaudi told Gizmodo. But WFIRST would also be the first to fly a technology in space that is important for two proposals for the next flagship space telescope: a “coronagraph.” A coronagraph is a device that blocks stars’ bright light, making the dimmer planets orbiting the star visible. If scientists hope to find life around other stars, they’ll need to image the light produced by and reflected by the planet directly. The issue is that the planet may be billions of times dimmer than the star it orbits. Scientists hope to one day spot Earth-like planets using this technology.
And here’s the most important part: Observing the light directly from planets, rather than just observing the periodic dimming produced when the planet passes in front of its star, could tell scientists whether the presence of life has altered the planet’s atmosphere the way it has on Earth. Climate change aside, life fills Earth’s atmosphere with carbon dioxide, oxygen, methane, and other biological building blocks. Therefore, determining whether life exists on other planets requires observing these planet’s atmospheres to see what molecules they contain.
Preparations for the 2020 Decadal Survey are already underway. Four teams of astronomers are preparing concept studies for WFIRST’s successor, a flagship telescope mission that would launch some time in the late 2030s or early 2040s. As happened in 2010, the survey will determine what astronomy’s most important scientific questions are, and how best to answer them using ambitious, potentially yet-to-be-developed technology. The decadal committee will move forward with a recommendation based on the goals and design of one or multiple concepts. It’s clear that hunting for signs of extraterrestrial life will play an enormous role in the discussion. Two of the concepts incorporate a coronagraph like WFIRSTs, and three list analysing exoplanets among their primary goals. All of them would cost billions of dollars.
The Large UV/Optical/IR Surveyor (LUVOIR) is the most ambitious of these four missions—and it would be truly enormous, with either an 8- or 15-meter mirror. It would be a sequel to JWST. Another, the Habitable Exoplanet Imaging Mission (HabEx), is built from the bottom up with observing exoplanets in mind. Both would rely on a coronagraph and a starshade, an external component that blocks the light of other stars.
Two other proposed telescopes wouldn’t rely on a coronagraph or a starshade. The Origins Space Telescope (OST) would look for exoplanets around cooler stars in the infrared wavelengths, where the difference in brightness between the star and planet isn’t as great. Its goals also include observing the formation of planets and the growing complexity of stars and galaxies. Finally, there’s Lynx, which is instead focused on high-energy astrophysical mysteries, such as the dawn of black holes and the birth and death of stars. It would be an x-ray telescope using sensitive instruments, and serve as the sequel to the wildly successful Chandra X-ray Telescope.
The National Academy of Sciences has already hinted that it favours a telescope equipped with a coronagraph or some sort of starlight-shading device, like LUVOIR or HabEx, when it comes to hunting for extraterrestrial life. From the recent Exoplanet Science Strategy report:
A coronagraphic or starshade-based direct imaging mission is the only path currently identified to characterise Earth-size planets in the habitable zones of a large sample of nearby Sun-like stars in reflected light… NASA should lead a large strategic direct imaging mission capable of measuring the reflected-light spectra of temperate terrestrial planets orbiting Sun-like stars.
Another more recent report from the National Academies outlining a strategy for the future of astrobiology calls starshades and coronagraphs “essential.”
It’s important to note that there a host of other Earth-based telescopes under development, like the Giant Magellan Telescope and the Thirty Meter Telescope. These ground-based telescopes are better for observing planets around cooler, small M-dwarf stars, Aki Roberge, scientist at the NASA Goddard Space Flight Center working on LUVOIR, recently told Gizmodo. Space telescopes equipped with starlight-blocking coronagraphs could better observe planets around Sun-like stars. Extraterrestrial life might exist on either, and both are part of a healthy astrobiology strategy.
The decadal space telescope proposals are already beginning to feel the heat from JWST. On June 1, NASA astrophysics director Paul Hertz emailed the concept teams, imposing a $US3 ($4) billion to $US5 ($7) billion cost goal for the studies. According to a press release, “With recent delays and budget constraints surrounding the two major flagship missions, the new direction will better ensure that the next flagship mission be executed on time and within budget.” However, he revised that memo two weeks later, and instead reminded teams that the second phase of their design process was beginning in which they should design a less costly architecture than their first designs. The National Academies has also recommended that these concepts think about cost and schedules. These concept studies are due to NASA by June 2019.
Some, like LUVOIR physicist John O’Meara, worry that the difficulties with JWST will cause members of the astronomy community to give up on large missions such as these in general. It’s a sentiment that some, like former NASA administrator Charles Bolden, have expressed before. “I hope they don’t do that,” said O’Meara.
“I’m really concerned about the state of funding,” Laura Lopez, assistant professor at Ohio State University working on the Lynx team, told Gizmodo. “It feels like a precarious situation where we don’t know what will happen next year, let alone in the next 15 years.” Any large missions like these would require sustained funding for more than a decade.
JWST could impact these future missions directly or based on how it affects WFIRST. This past summer, Congress has held hearings grilling NASA and Northrup Grumman about the JWST’s cost overruns and delays. Northrup Grumman CEO Wes Bush told Congressman Lamar Smith (R-Texas) that the company would not pick up the most recent $US800 ($1,128) million cost increase. It’s unclear what will happen next.
WFIRST faces clear threats. This past year, President Trump’s proposed budget included scrapping the telescope entirely. Scientists are confident that the more space-friendly Congress won’t let that happen, but Gaudi has heard talk threatening the existence of the coronagraph as well. Should WFIRST lose its coronagraph, scientists will miss an important opportunity to try the light-blocking technology out in space before flying it on the ultimate exoplanet-hunting telescope.
Gizmodo heard several times that flying a coronagraph without testing it on some previous mission could be a very bad idea with far-reaching implications on cost and schedule. “We may save roughly $US300 ($423) million by de-scoping a coronagraph,” David Spergel, Princeton astrophysicist working on WFIRST’s development, told Gizmodo, “but I suspect in the long run, it could cost a billion in development cost of LUVOIR or HabEx when the time comes to upgrade to a coronagraph capable of detecting Earth-like planets.” Gaudi said that flying a coronagraph on WFIRST would make LUVOIR or HabEx “much more palatable to pretty much everyone.”
Scientists have reminded Congress as to the coronagraph’s importance. “WFIRST’s coronagraph instrument is a technology demonstration,” Seager said recently at a Senate hearing. “It’s critical to do this to buy down more ambitious missions in the future already under study.”
For what it’s worth, the astronomers Gizmodo spoke with generally agree that JWST will be well worth the wait. But flagship telescopes are meant to advance significantly upon existing instruments—and improvement requires money. Scrapping or de-scoping WFIRST could further delay humanity’s dream to spot life on other planets, should the Decadal Survey ultimately decide to recommend a coronagraph-based mission. So, too, could fear or budgetary consequences stemming from the JWST delay.
Of course, what happens next with WFIRST is up in the air. Scientists are waiting to see what happens with the reconciliation of upcoming budgets, “and how Congress will respond to the additional delays of JWST,” said Gaudi. Given the country’s chaotic political climate, no one knows what will and won’t get funding in the future. But long-term investments require money—and representatives who are willing to allocate that money to support them.
“I’m just doing my best to provide Congress with as much information as I can so they make the best possible decision,” said Gaudi. “I hope they are ambitious and optimistic about the science.” | 0.833213 | 3.595267 |
Crescent ♐ Sagittarius
Moon phase on 30 September 2060 Thursday is Waxing Crescent, 5 days young Moon is in Sagittarius.Share this page: twitter facebook linkedin
Previous main lunar phase is the New Moon before 5 days on 24 September 2060 at 15:53.
Moon rises in the morning and sets in the evening. It is visible toward the southwest in early evening.
Moon is passing about ∠12° of ♐ Sagittarius tropical zodiac sector.
Lunar disc appears visually 7% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1787" and ∠1917".
Next Full Moon is the Hunter Moon of October 2060 after 9 days on 9 October 2060 at 18:41.
There is low ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at big angle, so their combined tidal force is weak.
The Moon is 5 days young. Earth's natural satellite is moving from the beginning to the first part of current synodic month. This is lunation 751 of Meeus index or 1704 from Brown series.
Length of current 751 lunation is 29 days, 17 hours and 32 minutes. It is 1 hour and 18 minutes shorter than next lunation 752 length.
Length of current synodic month is 4 hours and 48 minutes longer than the mean length of synodic month, but it is still 2 hours and 15 minutes shorter, compared to 21st century longest.
This New Moon true anomaly is ∠149.6°. At beginning of next synodic month true anomaly will be ∠174.6°. The length of upcoming synodic months will keep increasing since the true anomaly gets closer to the value of New Moon at point of apogee (∠180°).
2 days after point of apogee on 27 September 2060 at 17:42 in ♏ Scorpio. The lunar orbit is getting closer, while the Moon is moving inward the Earth. It will keep this direction for the next 9 days, until it get to the point of next perigee on 10 October 2060 at 10:18 in ♈ Aries.
Moon is 401 000 km (249 170 mi) away from Earth on this date. Moon moves closer next 9 days until perigee, when Earth-Moon distance will reach 357 605 km (222 205 mi).
3 days after its descending node on 26 September 2060 at 21:59 in ♎ Libra, the Moon is following the southern part of its orbit for the next 10 days, until it will cross the ecliptic from South to North in ascending node on 10 October 2060 at 13:33 in ♈ Aries.
17 days after beginning of current draconic month in ♈ Aries, the Moon is moving from the second to the final part of it.
12 days after previous North standstill on 17 September 2060 at 19:05 in ♊ Gemini, when Moon has reached northern declination of ∠28.029°. Next day the lunar orbit moves southward to face South declination of ∠-28.102° in the next southern standstill on 2 October 2060 at 10:31 in ♑ Capricorn.
After 9 days on 9 October 2060 at 18:41 in ♈ Aries, the Moon will be in Full Moon geocentric opposition with the Sun and this alignment forms next Sun-Earth-Moon syzygy. | 0.848363 | 3.090632 |
Do you have a new telescope, or are you considering buying a new one? Hopefully, you have chosen a telescope with the best specifications for your budget, but before you can truly get the best out of your wonderful new window on the cosmos, you need to have something even more important than the scope – Eyepieces!
A lot of people new to astronomy, or new to buying astronomy equipment tend to concentrate on telescopes and unfortunately overlook eyepieces, settling for the basic set of 2 or 3 that come with the new telescope.
Eyepieces are probably the most important part of your observing equipment, as they are at the heart of your setup and can make your observing experience fantastic or disastrous, or make an average telescope great or an excellent telescope bad.
Eyepieces are the part you look through and are responsible for magnification of the objects you see through the telescope. They come in many different magnifications and types, but it’s not rocket science. You will soon learn what works well for seeing different astronomical objects.
Telescope eyepieces are designed to fit into the focuser of the telescope. Depending on your telescope, they come in two sizes 1.25” or 2” and there is .965” which is an older size and pretty much obsolete, unless you have an old telescope. Most telescopes can be fitted with adapters so both sizes can be used.
The magnifying power of any Eyepiece is a simple equation expressed in millimetres: Divide the focal length of the telescope by the focal length of the Eyepiece and your answer is the amount of magnification. Long focal length eyepieces such as 32mm and 25mm are lower magnification, while lower numbers like 10mm and 5mm are magnifying powerhouses.
It is always good practice to start observing an object with a lower power Eyepiece such as a 40mm and gradually build up to higher powered eyepieces such as 10mm or lower. The reason for this is the telescope, human eye, seeing conditions and object being observed are all variable. Starting off with a high power such as 4.7mm may be a struggle.
Fainter objects such as nebula and galaxies are usually seen better with lower powers and you can really ramp up the power with bright objects like the moon.
Below are rough guides and are dependent on the telescope you use:
2mm-4.9mm Eyepieces: These are very high magnification and very difficult to use unless seeing conditions are perfect and the object observed is very bright, like the moon.
5mm – 6.9mm Eyepieces: These are good on bright objects such as the moon and bright planets, but are still very high power and work best with steady seeing conditions.
7mm – 9.9mm Eyepieces: These are very comfortable high magnification eyepieces and are excellent for observing brighter objects, a must for any eyepiece collection.
10mm – 13.9mm Eyepieces: These work well for all objects including brighter nebula and galaxies a good mid/high range magnification.
14mm – 17.9mm Eyepieces: These are a great mid range magnification and will help resolve globular clusters, galaxy details and planetary nebulae.
18mm – 24.9mm Eyepieces: These will work nicely to show wide field and extended objects, great mid-range magnification for objects like galaxy clusters and large open clusters.
25mm – 30.9mm Eyepieces: These are wider field eyepieces for large nebula and open clusters. A good finder eyepiece for locating objects before moving to higher powers.
31mm – 40mm Eyepieces: These are excellent for extended views and large star fields and make excellent finder eyepieces before moving to higher powers.
Eye relief is the distance from the last surface of an eyepiece at which the eye can obtain the full viewing angle. If a viewer’s eye is outside this distance, a reduced field of view will be obtained and viewing the image can be difficult. Generally longer eye relief is preferred.
Apparent Field of View
This is the apparent size of the image in the eyepiece and can range from about 35 to 100 degrees. Larger fields of view are more desired.
Types of Eyepiece
There are many different eyepiece types, some old and now obsolete, some simple and some advanced.
The different types are purely governed by the configuration of the glass and lenses inside the eyepiece. Some giving exceptional eye relief, wide fields of view, colour correction etc.
Some different brands include: Huygens, Ramsden, Kellner, Plössl, Orthoscopic and Kellner.
The most common and popular eyepiece type is the Plössl due to its good all round performance, good eye relief, approximate 50 degree field of view, pinpoint sharpness and good contrast. Plössl eyepieces are made by many manufacturers now, but there are excellent examples from manufacturers such as Meade and Televue.
Finally we have exotic eyepieces such as Super Wide and Ultra Wide which are usually 2” eyepieces, with higher powers up to around 4.7mm at 1.25” and are usually in the domain of the large Dobsonian or Newtonian telescope user, but are just at home on smaller telescopes such as refractors or Cassegrains.
These eyepieces sport amazing eye relief and huge “port hole” 80 – 100 degree views with fully loaded premium optics, which are very forgiving on telescopes with optical aberrations and other problems. They can make average or poor telescopes great, but there is a cost; an example of which is my 14mm Ultra Wide which cost £500 ($800) just for one eyepiece and I have a full set! Combined, my eyepieces are worth much, much more than the telescopes they are used on, but it’s worth it!
Eyepieces are the most important part of your observing equipment, choose them and use them well, which will help you enjoy observing through your telescope. Please view the different types and sizes of eyepiece in the Meteorwatch Store. | 0.828116 | 3.644016 |
On December 2, 02019, Professor Avi Loeb takes Long Now Boston to the frontiers of cosmic discovery and exobiology.
Professor Loeb is the Frank B. Baird, Jr. Professor of Science and Chair of Astronomy at Harvard, Director of the Institute for Theory and Computation, Founding Director of the Black Hole Initiative, Chair of both the Breakthrough Starshot Advisory Committee and the Board on Physics and Astronomy of the National Academies. In 2012, TIME magazine selected Loeb as one of the 25 most influential people in space science.
See post-event summary here: Life Among the Stars
December, 02019, at CIC, 1 Broadway, Cambridge MA
Doors open @ 6pm — Come early and meet other Long Now thinkers.
Presentations start @ 7pm
In the past few years, scientists have made huge progress probing ever more deeply into space. They have confirmed the existence of a vast multitude of earth-like planets. They have found evidence of complex chemistry in deep space and validated the claim that all life on Earth is made of stardust. Yet there is no evidence of life originating anywhere other than on Earth.
This may change soon. Upcoming searches will aim to detect markers of life in the atmospheres of planets outside the solar system. We also have unprecedented technologies to detect signs of intelligent civilizations through industrial pollution of planetary atmospheres, space archaeology of debris from dead civilizations or artifacts such as photovoltaic cells that are used to re-distribute light and heat on the surface of a planet or giant megastructures.
At the same time, we continue to launch interplanetary and even interstellar explorations of our own. Others may notice and seek to contact us — or we may find messages that confirm we are not alone.
Among the questions:
- What are some of the advanced scientific tools and techniques we are developing in the search for extraterrestrial life? How might these benefit other scientific disciplines?
- What are some of the explanations scientists have proposed to account for the discrepancy between the apparent readiness for life and the lack of evidence for life?
- What are the implications of finding extraterrestrial life? Of not finding it?
Abraham (Avi) Loeb is the Frank B. Baird, Jr. Professor of Science at Harvard University. He has published 4 books and over 700 papers on a wide range of topics, including black holes, the first stars, the search for extraterrestrial life and the future of the universe. He serves as chair of Harvard’s Department of Astronomy, founding director of Harvard’s Black Hole Initiative and director of the Institute for Theory and Computation within the Harvard-Smithsonian Center for Astrophysics. He is a Faculty Member of Harvard’s Origins of Life Initiative. He also chairs the advisory committee for the Breakthrough Starshot Advisory Committee, serves as the science theory director for all initiatives of the Breakthrough Prize Foundation, as well as chair of the Board on Physics and Astronomy of the National Academies. He is an elected fellow of the American Academy of Arts & Sciences, the American Physical Society, and the International Academy of Astronautics.
We’re proud and excited to welcome Avi to the Long Now Boston community.
Long Now Boston is a 501(c)(3) non-profit organization that is independent from but philosophically aligned with the Long Now Foundation. Long Now Boston provides a forum for discussing, investigating and engaging in issues that have long-term implications for our global cultures. Long Now Boston hosts a monthly Community Conversation series in Cambridge, MA. Please sign up on our website for notices.
Cambridge Innovation Center is an in-kind sponsor of the Long Now Boston Conversation Series. We are very grateful for their support.
On January 6 02020, Long Now Boston will hold its 2nd annual FLASH TALKS at the CIC, titled Envisioning the Future. Members are encouraged to submit FLASH TALK Proposals on issues of interest. The proposals will be reviewed, and up to six presenters will be selected to give a FLASH TALK. A prize valued at $100 will be given to the best presentation, selected by the audience. | 0.836488 | 3.193726 |
Minerals on Mars
Scientists have long wondered if Mars could support life. But what exactly should we look for?
“Biosignature” is a really cool word you hear a lot when people talk about finding life on other planets or moons. Because we’re looking for tiny microbes (that may have been dead for many millions or billions of years), scientists aren’t looking for life per se, but instead, signs of life — evidence of current or past living things, which is what a biosignature is.
Scientists have long wondered if Mars could support life, now or in the past. As far as the planets in our solar system go, it’s the most likely place, because water once flowed on its surface (and signs of super briny water flows remain today). But what exactly should we look for on Mars? It sounds like trying to find a microscopic needle in a very big haystack. NHM Mineral Science Curator Aaron Celestian is interested in the special role minerals play in this question. “How do you go to a different planet, zap a rock, and figure out that there are biosignatures in it?” he asks.
To help answer this question, Celestian is collaborating with Scott Perl, a research scientist at NASA’s Jet Propulsion Laboratory at Caltech who specializes in geobiology and astrobiology — the study of life on Earth and elsewhere in the universe. They’re considering what biosignatures we could potentially look for on the Martian surface. A likely biomarker (a specific chemical to test for) is a group of molecules called carotenoids, the most famous of which is beta-carotene — the pigment that makes carrots orange.
“Microbes on Earth use carotenoids to protect themselves from harmful UV light, and there is a great need for that on Mars because its atmosphere is so thin it doesn’t filter out the UV light coming from the sun,” said Celestian.
If microbes on Mars used (or use) similar pigments to protect themselves, they would be a very convenient biosignature for two reasons: 1) They don’t occur randomly on their own — they are only made by living things, and 2) They are easily identified among the minerals on the Martian surface with an instrument called a Raman spectrometer.
“Through our JPL, NHM, and USC Earth Sciences collaborations we’ve pioneered new methods to examine these chemical biomarkers,” said Perl.
The next NASA mission to Mars is called Mars 2020 — named after its destination and the year it will launch. It will send an SUV-sized rover to the Red Planet to learn more about our planetary neighbor, especially whether or not it has ever supported living things. And it just so happens to include a Raman spectrometer, the device that could potentially look for carotenoids in the Martian regolith (the scientific term for dirt on other planets and moons, since “soil” technically includes living things).
What are the odds of finding living things there? Celestian is an astrobiological optimist. “I am hopeful that there is a chance for living bacteria on Mars.”
Perl shares his optimism: “The minerals Aaron and I are investigating have the ability to protect microbial life and its biomarker evidence. If life were ever to have been present on Mars, I’m confident we can find it.” | 0.840818 | 3.793288 |
Nearby star hosts closest alien planet in the 'habitable zone'
UNSW Australia astronomers have discovered the closest potentially habitable planet found outside our solar system so far, orbiting a star just 14 light years away.
The planet, more than four times the mass of the Earth, is one of three that the team detected around a red dwarf star called Wolf 1061.
"It is a particularly exciting find because all three planets are of low enough mass to be potentially rocky and have a solid surface, and the middle planet, Wolf 1061c, sits within the 'Goldilocks' zone where it might be possible for liquid water—and maybe even life—to exist," says lead study author UNSW's Dr Duncan Wright.
"It is fascinating to look out at the vastness of space and think a star so very close to us—a near neighbour—could host a habitable planet.
"While a few other planets have been found that orbit stars closer to us than Wolf 1061, those planets are not considered to be remotely habitable," Dr Wright says.
The three newly detected planets orbit the small, relatively cool and stable star about every 5, 18 and 67 days. Their masses are at least 1.4, 4.3 and 5.2 times that of Earth, respectively.
The larger outer planet falls just outside the outer boundary of the habitable zone and is also likely to be rocky, while the smaller inner planet is too close to the star to be habitable.
The discovery will be published in The Astrophysical Journal Letters.
The UNSW team made the discovery using observations of Wolf 1061 collected by the HARPS spectrograph on the European Southern Observatory's 3.6 metre telescope in La Silla in Chile.
"Our team has developed a new technique that improves the analysis of the data from this precise, purpose-built, planet-hunting instrument, and we have studied more than a decade's worth of observations of Wolf 1061," says Professor Chris Tinney, head of the Exoplanetary Science at UNSW group.
"These three planets right next door to us join the small but growing ranks of potentially habitable rocky worlds orbiting nearby stars cooler than our Sun."
Small rocky planets like our own are now known to be abundant in our galaxy, and multi-planet systems also appear to be common. However most of the rocky exoplanets discovered so far are hundreds or thousands of light years away.
An exception is Gliese 667Cc which lies 22 light years from Earth. It orbits a red dwarf star every 28 days and is at least 4.5 times as massive as Earth.
"The close proximity of the planets around Wolf 1061 means there is a good chance these planets may pass across the face of the star. If they do, then it may be possible to study the atmospheres of these planets in future to see whether they would be conducive to life," says team member UNSW's Dr Rob Wittenmyer. | 0.881801 | 3.760532 |
A whiff of ammonia in reddish ices on Pluto may be evidence of recent geological activity on the dwarf planet, with liquid water spewing out from Pluto’s depths like molten lava would on Earth, a new study finds.
These findings suggest that Pluto may harbor at least some features favorable to the evolution of life, researchers said.
Scientists analyzed data that NASA’s New Horizons probe gathered during its flyby of the dwarf planet in 2015. In this data, they found evidence of ammonia on Pluto’s surface in areas that previous research suggested had experienced tectonic activity.
“In recent years, ammonia has been a bit like the ‘holy grail’ of planetary science,” study lead author Cristina Dalle Ore, a planetary scientist at NASA’s Ames Research Center in Moffett Field, California, told Space.com. One reason for this is that ammonia is a key ingredient in chemical reactions underlying life as we know it, “and therefore, when found, it flags [the presence of] an environment that is conducive to life. This does not mean that life is present — and we have not yet found it — but it indicates a place where we should look.”
Ammonia “is a fragile molecule and gets destroyed by ultraviolet irradiation as well as cosmic rays,” Dalle Ore said. “Therefore, when found on a surface, it implies that it had been emplaced there relatively recently, some million years before [being found].” | 0.83711 | 3.249149 |
A whole new side of Mercury hasbeen revealed in pictures taken by NASA's MESSENGER probe, which flew by thetiny planet two weeks ago in the first mission to Mercury in more than threedecades.
MESSENGER skimmed only 124 miles(200 kilometers) over Mercury's surface on Jan. 14, in the first of three passes it will make before settling into orbit March18, 2011.
The photos, released today,include one of a feature the scientists informally call "the spider,"which appears to be an impact crater surrounded by more than 50 cracks in thesurface radiating from its center.
Scientists are perplexed by thisstructure, which is unlike anything observed elsewhere in the solar system.
"It's a real mystery, a very unexpected find,"said Louise Prockter, an instrument scientist at the Johns HopkinsUniversity Applied Physics Laboratory, which built the probe for the $446million NASA mission. She said whatever event created the spider "isanybody's guess," but suggested perhaps a volcanic intrusion beneath theplanet's surface led to the formation of the troughs.
The last time NASA sent a probeto Mercury was in 1975, when the Mariner 10 spacecraft flew by the planet threetimes. MESSENGER'S first flyby gave scientists the first glimpses of Mercury'shidden side, the 55 percent of its surface that was left uncharted by Mariner10.
MESSENGER, short for MErcury Surface, Space ENvironment,GEochemistry, and Ranging, also measured another peculiar element of Mercury —its magnetic field. Earth has a magnetic field surrounding it that acts as aprotective bubble shielding the surface from cosmic rays and solar storms. Butscientists were shocked when Mariner 10 discovered a magnetic field at Mercury,too.
"The only other example in our solar system of an Earth-likemagnetosphere is tiny Mercury," said Sean C. Solomon, MESSENGER PrincipalInvestigator from the Carnegie Institution of Washington.
MESSENGER was able to fly through the magnetic field andtake detailed measurements that scientists hope to use to discover the originsof the inexplicable magnetosphere.
Scientists have been poring overmore than 1,200 new images sent by seven instruments on the probe, and they areexcited to gain new insight into the composition of Mercury's surface, theplanet's history, and whereits atmosphere comes from.
"On the eve of the encounter I couldn?t sleep atall," said Robert Strom, a MESSENGER science team member who also workedon the Mariner 10 mission. "I've waited 30 years for this. It didn?tdisappoint at all. I was astounded at the quality of these images. It dawned onme that this is a whole new planet that we're looking at."
The satellite will further probe Mercury'smysteries in a second pass over the planet in October, followed by a thirdflyby in September 2009.
The probe has traveled 4.9billion miles (7.9 billion-kilometers) since it launched in August 2004. On itsjourney it soared by Earth once and Venus twice, offering gorgeous views ofthese planets as well. In 2011 MESSENGER will become the first spacecraft toorbit the closest planet to the Sun.
- VIDEO: MESSENGER at Mercury
- IMAGES: Explore the Planet Mercury
- VIDEO: MESSENGER Probe Views Earth in Flyby | 0.859139 | 3.674224 |
A long time ago, in a galaxy far, far away…an unusually shaped object began its journey toward our solar system. Discovered on October 19, 2017 by the University of Hawaii’s PanSTARRS1 telescope, the first verified interstellar object was originally classified as a comet.
However, further observations revealed no cometary activity. It was then thought to be an unknown type of asteroid. But as it zipped past our sun, it accelerated slightly, leaving scientists scratching their heads.
Named Oumuamua by its discoverers, the first object known to come from outside out solar system was measured to be a quarter mile long. Observations confirmed it to be ten times as long as it is wide. Its unusual cigar shape is unlike any asteroid or comet so far discovered.
“For decades we’ve theorized that such interstellar objects are out there, and now—for the first time—we have direct evidence they exist,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate in Washington.
By using four different filters from the FORS instrument on the ESO Telescope, astronomers were able to determine that Oumuamua varies in brightness by a factor of ten as it spins on its axis every 7.3 hours.
“We also found that it had a reddish color, similar to objects in the outer solar system, and confirmed that it is completely inert, without the faintest hint of dust around it,” said Karen Meech of the Institute of Astronomy in Hawaii.
This suggests that the interstellar interloper is composed of rock and metals, making it very dense. Because no water-ice was detected, the most likely cause of its surface reddening is due to cosmic ray irradiation over hundreds of millions of years.
By studying the trajectory, astronomers have been able to deduce that Oumuamua likely came from the vicinity of the star Vega. But 300,000 years ago, when this unusual object made its journey from that area, Vega was not there.
This means that the Vega system is not the origin of our strange visitor.
“What a fascinating discovery this is! It’s a strange visitor from a faraway star system, shaped like nothing we’ve ever seen in our solar system neighborhood,” said Paul Chodas of the Center for Near-Earth Object Studies at NASA’s Jet Propulsion Laboratory.
Recent theories by a duo of researchers at Harvard Smithsonian Center for Astrophysics have raised the idea that Oumuamua might be artificial in origin.
The theory is based on its unexpected acceleration in January 2018, as it traveled through our solar system.
In a paper submitted to the Astrophysical Journal Letters, the two scientists wrote, “Oumuamua may be a fully operational probe sent intentionally to Earth vicinity by an alien civilization.
Light-sails with similar dimensions have been designed and constructed by our own civilization, including the IKAROS project and the Starshot Initiative. The light-sail technology might be abundantly used for transportation of cargos between planets or between stars.
This would account for the various anomalies of Oumuamua, such as the unusual geometry inferred from its light-curve, its low thermal emission, suggesting high reflectivity, and its deviation from a Keplerian orbit without any sign of cometary tail or spin-up torques.”
But Oumuamua isn’t the first-time astronomers have thought they’d found proof of extraterrestrial existence. Back in 1977, the WOW signal was detected by Ohio State University’s Big Ear telescope; the origins of which are still debated by scientists. And everyone has heard of Tabby’s Star: located in the constellation Cygnus about 1,470 light-years from Earth, whose brightness randomly fluctuates for unknown reasons, giving rise to theories of Dyson’s Spheres or an alien armada.
Fascinating theories aside, it is also possible that this visitor from afar is stellar fragment from a long ago violent super nova explosion, a piece of a rocky planet destroyed by an impact from another larger object, or any number of natural—as-of-yet unknown—origins. Just because an object like this hasn’t been detected in our solar system before, and its shape is unusual, doesn’t mean it is of artificial design.
There is so much about our cosmos that we still don’t know, so much to still be discovered.
With a fitting name meaning “a messenger from afar arriving first,” what are your thoughts on its origins? | 0.942952 | 3.935821 |
This is a single 30 second exposure taken with a 200mm telephoto lens at f/3.2 and ISO=400 with a Canon APS-H format camera; an iOptron SkyTracker equatorial drive was used for tracking. The time was 11:06 AM UT (4:06 AM local/mountain standard time) on Sept. 14, 2018.
North is up and east is to the left.
The comet (upper right in photo) was 1.70° away from the brightest star at the top of the core of the cluster (lower left) when this was taken. At an advertised angular rate of motion of 4.4 arc-minutes per hour, this puts the comet 23¼ hours away from this star, which coincides roughly with the predicted crossing-the-middle time of ~10 AM UT the 15th (4 AM MDT).
In all, it will take about four hours for the comet to cross the cluster, roughly from 1:30 a.m. MDT 'til 5:30 a.m., with dawn starting shortly thereafter. Over the four hours the comet will move 0.3°, or 60% the diameter of a full moon. It is moving through space at 8000 miles per hour.
The comet will only be 0.38 AU (35.6 million miles) from Earth. It is just a few days past it's perihelion on the 10th (and thus near its brightest) and a little over 1 AU from the Sun (1.023) -- just like the Earth -- so we will be roughly at the same point in space where it now is in a few weeks. Giacobini-Zinner is the parent body of the Draconid meteor shower (also known as the Giacobinids), which peaks Oct. 9th this year (6th - 10th in other years, depending).
This is the second best passage of Comet Giacobini-Zinner for us since its discovery in 1900. It has an orbital period of 6 5/8 years, and was 'lost' for two orbits until Zinner found it again in 1913 by accident (while studying variable stars).
The "P21" part of the designation says it was the 21st Periodic comet discovered. These are further sub-divided into short and long period groups, the arbitrary dividing line being at 200 years.
Michel Giacobini discovered several comets, one of which (#205P) went missing from 1896 until accidentally re-discovered by amateur supernova hunters in 2008 -- seventeen orbits later. In 1903, Giacobini received the Prix Jules Janssen (see Feb 22, 1824), the highest award of the French astronomical society. Giacobini was another scientist to be in a poison gas attack during WWI, but survived and went back to doing astronomy after the war, living until 1938 (age 65).
Comet Giacobini-Zinner is also famous for being the first comet ever visited by a spacecraft -- NASA's ICE, the International Cometary Explorer -- on Sep 11, 1985.
Messier 35 has a measured distance of 2,750 light-years (±50), or almost half a billion times farther than the comet. It is about 24 light-years in diameter. The much smaller and more distant cluster below and to the right of M35 is NGC 2158; it's orangeish color is partly due to the reddening effect of so much interstellar dust that we see it through at its much greater distance (6x), and partly because it contains more older, cooler, redder stars.
The comet crossing in front of M35 should be a fine spectacle for binoculars and small telescopes. At about 2 AM Mountain Daylight Time (or ½-1 hour later), both will be some 20° above the horizon and only slightly N of due E. Orion will be rising, and just clearing the horizon a little S of due E, then... so from the top star of Orion (Bellatrix, not brighter Betelgeuse below it) you'd want to go almost straight left (N) 22½° and up a few degrees until you get to the middle of the Milky Way. M35 and the comet should be right there. The darker your skies the better, and a clear E view would help in ID-ing Orion.
M35 is naked-eye visible for people with good eyesight under dark skies if you know where to look. Allow at least 15-20 minutes for complete dark adaptation. And no bright white flashlights (duh).
Fortunately, this pass of Comet G-Z took place during a really good stretch of weather, so I was able to get solid data on five of the six nights following this one, including the important first one (the 15th).
This first graph shows the sky background level for all the frames taken on four of the nights. The steep upturn at right in each is the onset of dawn. Only the last one (lower right) shows two little blips where there were evidently some thin clouds moving through over ~10-15 minutes. What's plotted is the simple frame average (roughly in the V band) for each 30 second exposure.
This second graph shows the sky background level for the 300 frames made during a nearly three hour run on the 18th, blown up so the noise can be seen.
The slight drifts, wiggles, and variations are barely above this level. It's not clear whether these are due to drifts in the equipment electronics or are real changes in the sky brightness, remembering that the field is not fixed in elevation because of equatorial mount tracking.
The slight downward slope at the start of the run might then be due to the field rising out of a sky slightly brighter towards the horizon, since it's darker closer to the zenith, all else being equal. The minimum about halfway through was when the field's elevation was ~41° (40°56'), or an airmass a little above 1½. At the end of astronomical night it was 55½ (1.21 air masses).
The low bump between that first one and the one closer towards the end of the run could then be due to a slightly different air mass drifting through and mixing overhead, especially because at its worst (peak of the hump) the noise level itself seems to go up noticeably.
One source of noise that's difficult to take into account is the result of the exposures not being guided. Polar misalignment causes the camera framing to drift very slowly with respect to the sky over long stretches like this. The practical effect is that stars slowly drift out of the field on one side of the frame while they're replaced by new stars drifting in on the opposite side. On average these should cancel each other out so there's no change, but only to the extent the density of stars on the sky in the region being photographed is constant. Just the fact that stars are discrete points means it isn't strictly constant, so there's going to be some noise just due to this. How much is difficult to say. Using the median rather than the mean (average) for the frame background level would largely eliminated this source of error.
The horizontal line is at a sky brightness level, in regular astronomical terms, of about 20½ magnitudes per square arc-second.
Here's a frame from the 16th (11:19 UT), when the comet was just 0.4° W of 3rd magnitude η (Eta) Geminorum, a triple star system:
η Geminorum is so near the ecliptic that it has been occulted by planets: Venus in 1910, and Mercury in 1837.
One of the things I noticed early on about this comet was that it was about a day ahead of the location shown for it in the planetarium program Stellarium (v.17.0 from early 2018); due to non-gravitational forces (outgassing, jets, etc.), comet positional observations often show a different set of orbital elements for each apparition.
All copyrights reserved. © 2018 C. Wetherill.
Main VISNS Page || The 2017 Total Solar Eclipse | 0.82819 | 3.643321 |
There’s always a twinkle in a science writer’s eye when real life imitates art.
Then in 2007 there came the news that the universe could be packed with double-sunned planets like Star Wars’ Tatooine.
With apologies to Sir Alec Guinness, this time that is a moon—Phobos is the larger of the two known natural satellites orbiting Mars.
—Image courtesy NASA/JPL-Caltech/University of Arizona
Although it was discovered way back in 1877, Phobos has remained fairly enigmatic.
In the late 1950s, its odd orbit inspired Russian astronomers to suggest that the moon is a hollow shell, and an artificial one at that.
It took almost a decade to silence that offbeat theory, based on better calculations of the moon’s orbit combined with new density measurements and eventually images from the Viking mission.
But Phobos still boasts some unusual characteristics, prompting much speculation about what the moon is made of and how it took up residence around Mars.
This week the European Space Agency released its newest images of Phobos taken by its Mars Express orbiter over a series of eight flybys.
—Image courtesy ESA/ DLR/ FU Berlin (G. Neukum)
The probe’s data on density and composition have ESA scientists “almost certain” that Phobos is a rubble pile, a loose collection of debris held together by gravity—and not a single, solid object.
If this is the case, it would support theories that Phobos and possibly also its “twin brother” moon Deimos are asteroids that got caught by Mars’s gravity. Another possibility is that they are lumped collections of debris that flew off Mars during an asteroid impact.
Oddly, one of the best pieces of supporting evidence for Phobos as rubble pile is its distinctively massive Stickney Crater.
On the surface it would seen reasonable to assume that an impact big enough to create a depression that size would have broken up a loose pile of rocks and scattered the debris to the cosmic wind.
But physics is phunny, and it turns out that such huge craters can exist only on weakly bound piles of stuff. That’s because the loose jumble actually dampens the propagation of shock waves after an impact, creating an indentation but allowing the overall structure to hold its shape.
It’s like the difference between shooting a gun at a rock versus firing at a sand dune. The bullet would shatter the solid rock into bits, but would merely put a dent in the sand.
With any luck, scientists should be able to put the story of Phobos’ origin to rest in the next few years. A planned Russian mission set to launch in 2009 aims to put a lander on the Martian moon and collect a soil sample to bring back to Earth for study. | 0.875966 | 3.805184 |
We have observed the G23 field of the Galaxy AndMass Assembly (GAMA) survey using the Australian Square Kilometre Array Pathfinder (ASKAP) in its commissioning phase to validate the performance of the telescope and to characterise the detected galaxy populations. This observation covers ~48 deg2 with synthesised beam of 32.7 arcsec by 17.8 arcsec at 936MHz, and ~39 deg2 with synthesised beam of 15.8 arcsec by 12.0 arcsec at 1320MHz. At both frequencies, the root-mean-square (r.m.s.) noise is ~0.1 mJy/beam. We combine these radio observations with the GAMA galaxy data, which includes spectroscopy of galaxies that are i-band selected with a magnitude limit of 19.2. Wide-field Infrared Survey Explorer (WISE) infrared (IR) photometry is used to determine which galaxies host an active galactic nucleus (AGN). In properties including source counts, mass distributions, and IR versus radio luminosity relation, the ASKAP-detected radio sources behave as expected. Radio galaxies have higher stellar mass and luminosity in IR, optical, and UV than other galaxies. We apply optical and IR AGN diagnostics and find that they disagree for ~30% of the galaxies in our sample. We suggest possible causes for the disagreement. Some cases can be explained by optical extinction of the AGN, but for more than half of the cases we do not find a clear explanation. Radio sources aremore likely (~6%) to have an AGN than radio quiet galaxies (~1%), but the majority of AGN are not detected in radio at this sensitivity. | 0.853325 | 3.742005 |
NASA’s Lunar Reconnaissance Orbiter is now within 20 kilometers of the lunar South Pole, the closest the spacecraft has ever been to the lunar surface.
On Monday, May 4, 2015 flight controllers at NASA’s Goddard Space Flight Center in Greenbelt, Maryland performed two station keeping burns to change LRO’s orbit. The new orbit allows LRO to pass within 20 km (12 miles) of the South Pole and 165 km (103 miles) over the North Pole.
“We’re taking LRO closer to the moon than we’ve ever done before, but the maneuver is similar to all other station keeping maneuvers, so the mission operations team knows exactly what to do,” said Steve Odendahl, LRO mission manager from NASA Goddard.
To optimize science return, team members made the decision to change the orbit after determining that the new orbit configuration poses no danger to the spacecraft. LRO can operate for many years at this orbit.
The new orbit enables exciting new science and will see improved measurements near the South Pole. Two of the instruments benefit significantly from the orbit change. The return signal from the Lunar Orbiter Laser Altimeter (LOLA) laser shots will become stronger, producing a better signal. LOLA will obtain better measurements of specific regions near the South Pole that have unique illumination conditions. Diviner will be able to see smaller lunar features through the collection of higher resolution data.
“The lunar poles are still places of mystery where the inside of some craters never see direct sunlight and the coldest temperatures in the solar system have been recorded,” said John Keller, LRO project scientist at NASA Goddard. “By lowering the orbit over the South Pole, we are essentially magnifying the sensitivity of the LRO instruments which will help us understand the mechanisms by which water or other volatiles might be trapped there.”
Launched on June 18, 2009, LRO has collected a treasure trove of data with its seven powerful instruments, making an invaluable contribution to our knowledge about the moon. LRO is managed by NASA’s Goddard Space Flight Center in Greenbelt, Maryland, for the Science Mission Directorate at NASA Headquarters in Washington.
For more information on LRO visit: http://www.nasa.gov/lro | 0.800694 | 3.001902 |
Hubble Space Telescope Views “El Gordo”
In 2014, astronomers using the NASA/ESA Hubble Space Telescope found that this enormous galaxy cluster contains the mass of a staggering three million billion Suns — so it’s little wonder that it has earned the nickname of “El Gordo” (“the Fat One” in Spanish)! Known officially as ACT-CLJ0102-4915, it is the largest, hottest, and X-ray brightest galaxy cluster ever discovered in the distant Universe.
Galaxy clusters are the largest objects in the Universe that are bound together by gravity. They form over billions of years as smaller groups of galaxies slowly come together. In 2012, observations from ESO’s Very Large Telescope, NASA’s Chandra X-ray Observatory and the Atacama Cosmology Telescope showed that El Gordo is actually composed of two galaxy clusters colliding at millions of kilometres per hour.
The formation of galaxy clusters depends heavily on dark matter and dark energy; studying such clusters can therefore help shed light on these elusive phenomena. In 2014, Hubble found that most of El Gordo’s mass is concealed in the form of dark matter. Evidence suggests that El Gordo’s “normal” matter — largely composed of hot gas that is bright in the X-ray wavelength domain — is being torn from the dark matter in the collision. The hot gas is slowing down, while the dark matter is not.
This image was taken by Hubble’s Advanced Camera for Surveys and Wide-Field Camera 3 as part of an observing programme called RELICS (Reionization Lensing Cluster Survey). RELICS imaged 41 massive galaxy clusters with the aim of finding the brightest distant galaxies for the forthcoming NASA/ESA/CSA James Webb Space Telescope (JWST) to study.
Credit: ESA/Hubble & NASA, RELICS
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The most extensive survey of atmospheric chemical compositions of exoplanets to date has revealed trends that challenge current theories of planet formation and has implications for the search for water in the solar system and beyond.
We’re seeing just how diverse extra-terrestrial worlds can be in terms of their chemical compositions
A team of researchers, led by the University of Cambridge, used atmospheric data from 19 exoplanets to obtain detailed measurements of their chemical and thermal properties. The exoplanets in the study span a large range in size - from ’mini-Neptunes’ of nearly 10 Earth masses to ’super-Jupiters’ of over 600 Earth masses - and temperature, from nearly 20C to over 2000C. Like the giant planets in our solar system, their atmospheres are rich in hydrogen, but they orbit different types of stars.
The researchers found that while water vapour is common in the atmospheres of many exoplanets, the amounts were surprisingly lower than expected, while the amounts of other elements found in some planets were consistent with expectations. The results , which are part of a five-year research programme on the chemical compositions of planetary atmospheres outside our solar system, are reported in The Astrophysical Journal Letters.
"We are seeing the first signs of chemical patterns in extra-terrestrial worlds, and we’re seeing just how diverse they can be in terms of their chemical compositions," said project leader Dr Nikku Madhusudhan from the Institute of Astronomy at Cambridge, who first measured low water vapour abundances in giant exoplanets five years ago.
In our solar system, the amount of carbon relative to hydrogen in the atmospheres of giant planets is significantly higher than that of the sun. This ’super-solar’ abundance is thought to have originated when the planets were being formed, and large amounts of ice, rocks and other particles were brought into the planet in a process called accretion.
The abundances of other elements have been predicted to be similarly high in the atmospheres of giant exoplanets - especially oxygen, which is the most abundant element in the universe after hydrogen and helium. This means that water, a dominant carrier of oxygen, is also expected to be overabundant in such atmospheres.
The researchers used extensive spectroscopic data from space-based and ground-based telescopes, including the Hubble Space Telescope, the Spitzer Space Telescope, the Very Large Telescope in Chile and the Gran Telescopio Canarias in Spain. The range of available observations, along with detailed computational models, statistical methods, and atomic properties of sodium and potassium, allowed the researchers to obtain estimates of the chemical abundances in the exoplanet atmospheres across the sample.
The team reported the abundance of water vapour in 14 of the 19 planets, and the abundance of sodium and potassium in six planets each. Their results suggest a depletion of oxygen relative to other elements and provide chemical clues into how these exoplanets may have formed without substantial accretion of ice.
"It is incredible to see such low water abundances in the atmospheres of a broad range of planets orbiting a variety of stars," said Madhusudhan.
"Measuring the abundances of these chemicals in exoplanetary atmospheres is something extraordinary, considering that we have not been able to do the same for giant planets in our solar system yet, including Jupiter, our nearest gas giant neighbour," said Luis Welbanks, lead author of the study and PhD student at the Institute of Astronomy.
Various efforts to measure water in Jupiter’s atmosphere, including NASA’s current Juno mission, have proved challenging. "Since Jupiter is so cold, any water vapour in its atmosphere would be condensed, making it difficult to measure," said Welbanks. "If the water abundance in Jupiter were found to be plentiful as predicted, it would imply that it formed in a different way to the exoplanets we looked at in the current study."
"We look forward to increasing the size of our planet sample in future studies," said Madhusudhan. "Inevitably, we expect to find outliers to the current trends as well as measurements of other chemicals."
These results show that different chemical elements can no longer be assumed to be equally abundant in planetary atmospheres, challenging assumptions in several theoretical models.
"Given that water is a key ingredient to our notion of habitability on Earth, it is important to know how much water can be found in planetary systems beyond our own," said Madhusudhan.
L. Welbanks, N. Madhusudhan, N. Allard, et al. ’ Mass-Metallicity Trends in Transiting Exoplanets from Atmospheric Abundances of H2O, Na, and K.’ The Astrophysical Journal Letters (2019). DOI: 10.3847/2041-8213/ab5a89
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More news on dark matter this week: By analyzing light from dwarf galaxies that orbit the Milky Way, scientists believe they have discovered the minimum mass for galaxies in the universe – 10 million times the mass of the sun. This mass could be the smallest known “building block†of the mysterious, invisible substance called dark matter. Stars that form within these building blocks clump together and turn into galaxies. Scientists know very little about the microscopic properties of dark matter, even though it accounts for approximately five-sixths of all matter in the universe. “By knowing this minimum galaxy mass, we can better understand how dark matter behaves, which is essential to one day learning how our universe and life as we know it came to be,†said Louis Strigari, lead author of this study from the University of California, Irvine.
Dark matter governs the growth of structure in the universe. Without it, galaxies like our own Milky Way would not exist. Scientists know how dark matter’s gravity attracts normal matter and causes galaxies to form. They also suspect that small galaxies merge over time to create larger galaxies such as our Milky Way.
The smallest known galaxies, called dwarf galaxies, vary greatly in brightness, from 1,000 times the luminosity of the sun to 10 million times the luminosity of the sun. At least 22 of these dwarf galaxies are known to orbit the Milky Way. UCI scientists studied 18 of them using data obtained with the Keck telescope in Hawaii and the Magellan telescope in Chile, with the goal of calculating their masses. By analyzing stars’ light in each galaxy, they determined how fast the stars were moving. Using those speeds, they calculated the mass of each galaxy.
The researchers expected the masses to vary, with the brightest galaxy weighing the most and the faintest galaxy weighing the least. But surprisingly all dwarf galaxies had the same mass – 10 million times the mass of the sun.
Manoj Kaplinghat, a study co-author and physics and astronomy assistant professor at UCI, explains this finding using an analogy in which humans play the role of dark matter.
“Suppose you are an alien flying over Earth and identifying urban areas from the concentration of lights in the night. From the brightness of the lights, you may surmise, for example, that more humans live in Los Angeles than in Mumbai, but this is not the case,†Kaplinghat said. “What we have discovered is more extreme and akin to saying that all metro areas, even those that are barely visible at night to the aliens, have a population of about 10 million.â€
Since dwarf galaxies are mostly dark matter – the ratio of dark matter to normal matter is as large as 10,000 to one – the minimum-mass discovery reveals a fundamental property of dark matter.
“We are excited because these galaxies are virtually invisible, yet contain a tremendous amount of dark matter,†said James Bullock, a study co-author and director of UCI’s Center for Cosmology. “This helps us better understand the particle that makes up dark matter, and it teaches us something about how galaxies form in the universe.â€
The scientists say clumps of dark matter may exist that contain no stars. The only dark matter clumps they can detect right now are those that are lit by stars.
Scientists hope to learn about dark matter’s microscopic properties when the Large Hadron Collider in Switzerland becomes operational later this year. The device will accelerate two beams of nuclei in a ring in opposite directions and then slam them together to recreate conditions just after the Big Bang. By doing this, scientists hope to create the dark matter particle in the lab for the first time.
Source: University of California, Irvine | 0.845951 | 3.85923 |
(April 9th, 2020: Please see the end of this caption for an added note discussing the possibility of systematic errors.)
This graphic contains a map of the full sky and shows four of the hundreds of galaxy clusters that were analyzed to test whether the Universe is the same in all directions over large scales, as described in our latest press release. Galaxy clusters are the largest objects in the Universe bound by gravity and astronomers can use them to measure important cosmological properties. This latest study uses data from NASA's Chandra X-ray Observatory and ESA's XMM-Newton to investigate whether or not the Universe is "isotropic."
The sky map in this schematic is in "galactic coordinates," with the plane of the Milky Way running along the middle (instead of the equator like is used for Earth). Galactic longitude runs in the horizontal, or "x" direction, and galactic latitude runs in the vertical, or "y" direction. The dark points show the location in the sky map of the 313 galaxy clusters observed with Chandra and XMM-Newton and included in this study. The four Chandra images of galaxy clusters from the new study are, in a clockwise direction from the top left, Abell 2199, RXCJ1504.1-0248, Abell 3667 and Abell 85. Galaxy clusters with galactic latitudes less than 20 degrees were not included in the survey to avoid obscuration from the Galaxy itself, which has most of its stars, gas and dust along a thin plane. Similarly, galaxy clusters behind two nearby galaxies, the Small Magellanic Cloud and the Large Magellanic Cloud, and behind the Virgo galaxy cluster were not included to avoid obscuration.
Astronomers generally agree that after the Big Bang, the cosmos has continuously expanded like a baking loaf of raisin bread. As the bread bakes, the raisins (which represent cosmic objects like galaxies and galaxy clusters) all move away from one another as the entire loaf (representing space) expands. With an even mix the expansion should be uniform in all directions, as it should be with an isotropic Universe.
This latest test uses a powerful, novel and independent technique and suggests the concept of an isotropic Universe may not entirely fit. The study capitalizes on the relationship between the temperature of the hot gas pervading a galaxy cluster and the amount of X-rays it produces, known as the cluster's X-ray luminosity. The higher the temperature of the gas in a cluster, the higher the X-ray luminosity is. Once the temperature of the cluster gas is measured, the X-ray luminosity can be estimated. This method is independent of cosmological quantities, including the expansion speed of the Universe.
Once they estimated the X-ray luminosities of their clusters using this technique, scientists then calculated luminosities using a different method that does depend on cosmological quantities, including the Universe's expansion speed. The results gave the researchers apparent expansion speeds across the whole sky — revealing that the Universe appears to be moving away from us faster in some directions than others.
The authors of this new study came up with two possible explanations for their results that involve cosmology. One of these explanations is that large groups of galaxy clusters might be moving together, but not because of cosmic expansion. For example, it is possible some nearby clusters are being pulled in the same direction by the gravity of groups of other galaxy clusters. If the motion is rapid enough it could lead to errors in estimating the luminosities of the clusters.
A second possible explanation is that the Universe is not actually the same in all directions. One intriguing reason could be that dark energy — the mysterious force that seems to be driving acceleration of the expansion of the Universe — is itself not uniform. In other words, the X-rays may reveal that dark energy is stronger in some parts of the Universe than others, causing different expansion rates.
Either of these two cosmological explanations would have significant consequences. The astronomical community must perform other scrutinized tests obtaining consistent results every time to truly know if the concept of an isotropic Universe should be reconsidered.
A paper describing these results will appear in the April 2020 issue of the journal Astronomy and Astrophysics and is available online. The authors are Konstantinos Migkas (University of Bonn, Germany), Gerrit Schellenberger (Center for Astrophysics | Harvard & Smithsonian), Thomas Reiprich, Florian Pacaud and Miriam Elizabeth Ramos-Ceja (University of Bonn), and Lorenzo Lovisari (CfA).
NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.
Added note (April 9th, 2020): In the original posting of this caption and the press release we did not mention the possibility of "systematic errors" explaining some or all of these results, rather than the two cosmological explanations we discuss. First author Konstantinos Migkas had explained an example of a possible systematic error in his blog post that accompanied the press release. A relevant excerpt is here:
"So did we tear down one of the most crucial pillars of cosmology? Not so fast, it is not that simple. At least two scenarios may have led us to wrong conclusions.
Firstly, cosmic material might interfere with the light that travels from the clusters to the Earth. For example, previously unknown gas and dust clouds beyond the Milky Way could obscure a fraction of photons emitted from the clusters. Since we ignore the possible existence of such clouds, we do not account for their interference, and hence we would falsely underestimate the true luminosity of the clusters. Eventually, we could mistake this for a cosmological effect. We performed several tests that led us to believe that this scenario seems unlikely, but not impossible. However, considering that the direction of the anisotropy we find agrees with other studies that used observations in light at different wavelengths, where such obscuring effects are not expected, one could argue against the possibility of such biases in our analysis."
Their peer reviewed and published paper considers this and several other possible systematic errors in detail, and will address other possibilities in a future peer-reviewed paper.
|Fast Facts for Abell 2199:|
|Credit||NASA/CXC/Univ. of Bonn/K. Migkas et al.|
|Release Date||April 8, 2020|
|Scale||Image is about 15 arcminutes (1.8 million light years) across.|
|Category||Cosmology/Deep Fields/X-ray Background, Groups & Clusters of Galaxies|
|Coordinates (J2000)||RA 16h 28m 38.50s | Dec 39° 33´ 03"|
|Observation Date||6 pointings between December 1999 through November 2009|
|Observation Time||44 hours (1 day 20 hours)|
|Obs. ID||497-498, 10748, 10803-10805|
|References||Migkas, K. et al., 2020, A&A; arXiv:2004.03305|
|Color Code||X-ray: Magenta|
|Distance Estimate||About 410 million Light Years (z=0.030)| | 0.83743 | 3.899877 |
Astronomers recently discovered a quiescent black hole in a distant galaxy that erupted after shredding and devouring a passing star. And now in a new finding, researchers have identified a distinctive X-ray signal observed in the days following the outburst that comes from matter on the verge of falling into the black hole.
“This tell-tale signal, called a quasi-periodic oscillation or QPO, is a characteristic feature of the accretion disks that often surround the most compact objects in the universe — white dwarf stars, neutron stars and black holes. QPOs have been seen in many stellar-mass black holes, and there is tantalizing evidence for them in a few black holes that may have middleweight masses between 100 and 100,000 times the sun’s.”
Until now, QPOs had only been detected from one supermassive black hole. Super massive black holes are the size of millions of solar masses and are usually located at the centers of galaxies. “That object is the Seyfert-type galaxy REJ 1034+396, which at a distance of 576 million light-years lies relatively nearby.”
“This discovery extends our reach to the innermost edge of a black hole located billions of light-years away, which is really amazing. This gives us an opportunity to explore the nature of black holes and test Einstein’s relativity at a time when the universe was very different than it is today,” said Rubens Reis, an Einstein Postdoctoral Fellow at the University of Michigan in Ann Arbor.
“Reis led the team that uncovered the QPO signal using data from the orbiting Suzaku and XMM-Newton X-ray telescopes, a finding described in a paper published August 2 in Science Express.”
“The X-ray source known as Swift J1644+57 — after its astronomical coordinates in the constellation Draco — was discovered on March 28, 2011, by NASA’s Swift satellite. It was originally assumed to be a more common type of outburst called a gamma-ray burst, but its gradual fade-out matched nothing that had been seen before. Astronomers soon converged on the idea that what they were seeing was the aftermath of a truly extraordinary event — the awakening of a distant galaxy’s dormant black hole as it shredded and gobbled up a passing star. The galaxy is so far away that light from the event had to travel 3.9 billion years before reaching Earth.”
“The star experienced intense tides as it reached its closest point to the black hole and was quickly torn apart. Some of its gas fell toward the black hole and formed a disk around it. The innermost part of this disk was rapidly heated to temperatures of millions of degrees, hot enough to emit X-rays. At the same time, through processes still not fully understood, oppositely directed jets perpendicular to the disk formed near the black hole. These jets blasted matter outward at velocities greater than 90 percent the speed of light along the black hole’s spin axis. One of these jets just happened to point straight at Earth.”
“Nine days after the outburst, Reis, Strohmayer and their colleagues observed Swift J1644+57 using Suzaku, an X-ray satellite operated by the Japan Aerospace Exploration Agency with NASA participation. About ten days later, they then began a longer monitoring campaign using the European Space Agency’s XMM-Newton observatory.”
“Because matter in the jet was moving so fast and was angled nearly into our line of sight, the effects of relativity boosted its X-ray signal enough that we could catch the QPO, which otherwise would be difficult to detect at so great a distance,” said Tod Strohmayer, an astrophysicist and co-author of the study at NASA’s Goddard Space Flight Center in Greenbelt, Md.
“As hot gas in the innermost disk spirals toward a black hole, it reaches a point astronomers refer to as the innermost stable circular orbit (ISCO). Any closer to the black hole and gas rapidly plunges into the event horizon, the point of no return. The inward spiraling gas tends to pile up around the ISCO, where it becomes tremendously heated and radiates a flood of X-rays. The brightness of these X-rays varies in a pattern that repeats at a nearly regular interval, creating the QPO signal.”
“The data show that Swift J1644+57’s QPO cycled every 3.5 minutes, which places its source region between 2.2 and 5.8 million miles (4 to 9.3 million km) from the center of the black hole, the exact distance depending on how fast the black hole is rotating. To put this in perspective, the maximum distance is only about 6 times the diameter of our sun. The distance from the QPO region to the event horizon also depends on rotation speed, but for a black hole spinning at the maximum rate theory allows, the horizon is just inside the ISCO.”
“QPOs send us information from the very brim of the black hole, which is where the effects of relativity become most extreme,” Reis said. “The ability to gain insight into these processes over such a vast distance is a truly beautiful result and holds great promise.”
Image Credits: NASA’s Goddard Space Flight Center; Black Hole | 0.856834 | 4.068192 |
Hydrogen-spewing volcanoes could boost the temperatures of seemingly frigid alien planets enough to maintain liquid water on their surfaces, making the worlds potentially habitable to life as we know it, a new study suggests.
If the newfound TRAPPIST-1h — the most distant of a set of seven Earth-size worlds that orbit a dwarf star just 39 light-years from Earth — boasted such volcanoes, it could be warm enough to hold onto water, study team members said.
In the past, scientists determined that the "habitable zone" — the range of distances from a star that can support liquid water on a world's surface — expands when planets have hydrogen in their atmospheres. However, because hydrogen is such a light gas, it quickly escapes to space, leaving such planets devoid of it within a few tens of millions of years. [5 Amazing Facts About the TRAPPIST-1 System (Video)]
But active volcanoes could change that, according to the new study.
"Our volcanic-hydrogen habitable zone is different, because so long as volcanism is intense enough, it can outpace the rate at which hydrogen escapes into space," lead author Ramses Ramirez, a planetary scientist at Cornell University in New York, told Space.com by email.
Ramirez and fellow planetary scientist Lisa Kaltenegger, also at Cornell, examined how active hydrogen-rich volcanos could continue to resupply a planet with a hydrogen atmosphere. They found the activity could increase the size of the habitable zone by as much as 60 percent, dramatically extending the region where habitable planets might lie.
According to Ramirez, the increased volcanism "allows potentially habitable conditions for much longer geologic timescales."
Improving the odds
The hunt for signs of life on worlds beyond the solar system tends to focus on the habitable zone, because water is crucial to life as we know it. (While other evolutionary paths are possible, scientists prefer to focus on the one known to have succeeded at least once.)
While studying possibilities for early Mars, Ramirez and Kaltenegger realized that massive outgassing of hydrogen early in the life of the Red Planet could have made for a warmer, wetter world.
"I liked the idea enough that I decided to extend it to the habitable zone," Ramirez said.
The process works well for small planets like Mars, where internal processes would keep the mantle hydrogen-rich. When volcanoes spew lava from the mantle, they can release hydrogen and hydrogen-rich gases into the atmosphere. A hydrogen-rich atmosphere could bump out the outer edge of the habitable zone by as much as 60 percent, giving more worlds the opportunity to hold onto their life-giving water, Ramirez and Kaltenegger said.
That doesn’t mean larger worlds are out of luck. While massive super-Earths are more likely to release hydrogen-poor gases into the air, they could still have enough volcanoes spewing material to outpace the escape of hydrogen into space. Such large worlds also have gravity on their side and are more likely to boast magnetic fields, both of which slow down hydrogen's escape into space.
The exact properties of these volcanoes would depend on their home planet. A planet's mass (which affects how strongly gravity tugs at the lava) and whether it has plate tectonics play key roles in building its volcanoes. On Earth, collision and disruption of the crust through tectonics mix up the material that becomes the lava, creating a variety of chemical compositions. On Mars, where gravity is low and the crust is a single large plate, Ramirez said, volcanic material is less evolved, and the lava flows pile up to create huge volcanoes, including the largest in the solar system, Olympus Mons. [Supervolcanoes Found On Mars (Video)]
Dense hydrogen atmospheres on alien worlds could still bear a strong similarity to Earth's. That could have implications for our young planet, Ramirez said.
"One idea suggested that hydrogen gas concentrations may have been high on the early Earth," he said. (Today, hydrogen is but a trace component of Earth's atmosphere, which is 78 percent nitrogen and 21 percent oxygen.) "If that hypothesis is true, early Earth may have resembled these hydrogen-rich exoplanets."
The research was published in the Astrophysical Journal Letters.
The hunt for life
Last week, scientists announced the discovery of the TRAPPIST-1 system, a series of seven rocky worlds, each about the same size as Earth, around a dwarf star. At least three of the worlds appear to fall within the habitable zone, assuming they have Earth-like atmospheres.
TRAPPIST-1h, the most distant of the seven worlds, seems to be out in the cold. But if the small planet has volcanoes venting hydrogen gas, it could just make the cut for habitability, study team members said.
According to Ramirez, TRAPPIST-1h lies just outside the new volcanic hydrogen habitable zone.
"But it is really close," he said. If volcanoes on the planet released a bit more hydrogen than the team’s models call for, it could hold onto liquid water, he added.
That could mean good news in the hunt for life. Because the TRAPPIST-1 system lies only 39 light-years from Earth, it will make a good target for studying the atmospheres of planets with observatories like NASA's $8.8 billion James Webb Space Telescope, which is scheduled to launch in late 2018.
Exoplanet atmospheres are beginning to release their secrets. When a world passes between Earth and its star, the planet's atmosphere absorbs some of the light, allowing scientists to study the atmosphere's composition.
Even if "biosignature" gases were found in a planet’s atmosphere, it could still be a challenge to determine if they were produced by living organisms or through other processes, Ramirez said. Still, just locating the signatures would be easier with volcanically active worlds, since hydrogen "puffs up" the atmosphere around a planet, creating a larger atmospheric signal that would be easier to study.
"Biosignatures would be easier to detect in these hydrogen-rich atmospheres," Ramirez said. | 0.909769 | 3.896468 |
Neptune's original family of satellites may have been destroyed when its largest moon, Triton, entered the picture. New research suggests that the massive moon may have tossed some of the original satellites into the ice giant, kicked others out of orbit and swallowed up the rest, creating a new family that doesn't look much like those surrounding the other giant planets.
For years, scientists have suspected that Triton wasn't part of Neptune's original collection of moons. The massive moon has a backward orbit, and makes up over 99 percent of all the mass orbiting the planet. Instead, they thought it was a captured object whose orbit was circularized by debris disks created by impacts.
New research suggests that the crashing primordial moons wouldn't have built up enough material to slow down Triton. [Living on Triton: Neptune's Moon Explained (Infographic)]
"We find that the mutual impacts between satellites are not disruptive enough to create the desired debris disk," Raluca Rufu, a doctoral student at the Weizmann Institute of Science in Israel, told Space.com by email. Working with co-author Robin Canup, a researcher and associate vice president at the Southwest Research Institute in Colorado who models solar system evolution and collisions, Rufu is lead author on new research that suggests Triton likely sent Neptune's original satellites flying.
The moons of Jupiter, Saturn and Uranus are all well-behaved compared with those of Neptune. The other three gas giants have a wealth of satellites — Jupiter has 70 to Neptune's 14, for instance — traveling in nearly circular paths around their equators. While Triton's path is circular, it travels backward compared with Neptune's rotation, and spins backward, besides.
And Triton is not the only outlier at Neptune. Nereid, one of the planet's outermost moons and the third largest, has one of the most stretched out, or eccentric, orbits of any moon in our solar system. It takes 360 Earth-days for the tiny moon to make one loop around its planet.
The unusual combination of moons led scientists to suggest that Triton was part of a pair of objects from the edge of the solar system that burst into the Neptunian system.
"The leading theory of Triton's capture is that Triton was part of a binary system, similar to Pluto and Charon," Rufu said. "Triton was captured while the secondary body escaped Neptune's gravitational pull."
Rufu and Canup modeled a Neptunian family similar to the other gas giants, then had Triton crash the party. Over time, the extended orbit of a captured satellite should settle into the more circular orbit seen today, through interactions with other moons and small objects.
Previous studies had shown that Triton's irregular orbit needed to settle down within a hundred thousand years, or irregular satellites like Nereid would have been tossed out, the researchers said. Rufu and Canup found it wasn't enough for Triton to just collide with the small satellites after it was captured—it had to throw some of the moons out, as well.
Instead of modeling an interloper that settled in smoothly with its new family, they crashed Triton into other, smaller satellites, sending many of them flying. The energy from the impacts knocked the rough edges off Triton's orbit, allowing it to succumb to Neptune's gravitational tugs and become more circular.
While some of the original satellites were hurled into space or swallowed up by Neptune, others may have been absorbed by Triton itself.
"If we want to look for the primordial Neptunian satellites, my best guess would be to look inside Triton," Rufu said. She warned that the energetic impacts could melt the satellites, removing any observable craters and making the primordial pieces more challenging to identify.
It's too bad for Neptune's original satellites that the ice giant didn't start out with more moons. Rufu and Canup found that a more massive primordial family could have meant doom for Triton. As long as the mass of the original satellite system was comparable to Uranus, which has only 27 moons, Triton would dominate, wreaking havoc as a homewrecker. But if the original system had contained a more massive moon, Triton may not have stood a chance. According to Rufu, a collision with a large enough satellite in a prograde orbit, along the same path as the planet's rotation, would have thrown Triton into Neptune.
"A massive prograde moon [could] decrease Triton's speed too much, and lead to Triton's fall," Rufu said.
The research was detailed Nov. 6 in The Astronomical Journal. | 0.841475 | 3.791552 |
Almost everything that Sam and his friends see moving, on the Earth or in the sky, is obeying Sir Isaac Newton’s Theory of Gravity and Laws of Motion.The Theory of Gravity says that everything in the whole Universe is attracting everything else, with a force which depends upon their mass and the distance between them, and by everything I do mean everything, even you and Sam! But fortunately neither of you are very big and you are not very close to each other so neither of you notice the (purely gravitational!) attraction you have for each other. But the Earth is very big and you are very close to it so you do notice the attraction between you and it - it is called your weight!
If you are about Sam’s age you probably have a mass of somewhere between 30 and 50 kg. The Moon is much smaller than the Earth so Moon gravity is much less than Earth gravity. If you go to the Moon you do not suddenly get so thin that none of your clothes fit, it is your weight (that is, the force of gravity on you) that has changed not your mass. On the surface of the Earth many people use mass and weight to mean the same thing but you must not do this anywhere else.
The Earth and the Sun may be millions of kilometres away from each other but the Sun is very big indeed so there is a very big gravitational force between them.
Newton’s Second Law of Motion says that if something is not moving we need a force to make it move, and if it is moving we need a force to make it move faster or more slowly or in a different direction. Sam has never played golf but he knows that the ball does not move until you hit it, and he has played beach tennis and knows that you need to hit the ball hard to return it (make it go back to the other end, that is, make it move in a totally different direction).Sam realises that this means that if something is moving in a circle we need a force to keep it moving in a circle. One day he stuffs some old T-shirts into an old pillow case and makes them into a soft bundle on the end of a rope. He and his friends go onto the beach - they take a plastic bucket with their lunch in it as well as the rope and the bundle. On the beach they start swinging the bundle round in a circle. They can feel a force in the rope, the faster they swing it the bigger the force, it can be several times the weight of the bundle.
We sometimes call this force the centrifugal force, from the Latin for fleeing from the centre, but if we let go of the rope this is not actually what happens, the bundle goes on in a straight line not straight outwards from the centre.
They do the same with the bucket filled with sea water - but stand well clear: if it hits you a bucket of water will hurt you much more than a bundle of clothes and make you very wet.
Adults (if you have not done this before it is best to practise beforehand wearing swimmers) can sometimes make the bucket go right over their heads without the water falling out. Children cannot often do this, they have to use a shorter rope so they must make the bucket go faster.
We can also feel a force when we go round a bend in a road too quickly: we may feel we are being thrown out of the car, but in fact there is no force trying to throw us out, what we feel is the force of the car on us trying to make us stay in the car rather than continue in a straight line. The tighter the curve and the faster we go round it the bigger the force needed to keep us in the car.
We often compare the forces acting on our body with the normal force of gravity on our bodies when we are on the surface of the Earth - this is 1 g (g for gravity not grams!). On a roller coaster, at the bottom of each loop we experience a force of more than 1 g, so there is a force pushing us down harder into our seat, as we go over the top of each loop we experience a force of less than 1 g, so we might be lifted out of our seat if we are not strapped in.
If you watch motor racing on tv you may sometimes see the g-force meter on the instrument panel: try watching it on a high-speed curve!
You can find out for yourself what would happen if you do not wear a seat belt in a car by using your Mum’s food blender without first putting the lid on - but ask first. On a spin dryer the water is thrown out through the holes in the drum, but the clothes are too big to go through the holes so they stay inside.
The Earth is going round the Sun, so there must be a force acting on it to stop it from flying off in a straight line into space: this force is the gravitational force between the Earth and the Sun - the two exactly balance! And the same for all the other planets.
This is also the reason why the Moon and television satellites and GPS satellites and the International Space Station go round the Earth. But remember that when we are calculating their orbits we must not forget that they are also being affected by the Sun’s gravity as well as the Earth’s.
The ISS stays in its orbit round the Earth because the force needed to keep it from flying off in a straight line into outer space is exactly equal to the force of gravity between it and the Earth. And what is true of the ISS is also true of everything inside it, even you. If you are holding a jug of water and let go of it it will stay in the same orbit, if you turn the jug upside down you will not change the orbit of the water inside it: you and everything inside or even outside the ISS are weightless - true zero g! But remember your mass has not changed even though the bathroom scales are just floating around in space just like you. If you accidently let go of your Hasselblad camera (value more than ten thousand pounds) while you are working outside the ISS - and this really has happened - it will stay in orbit long after you have returned to the Earth.
When an aircraft pulls out of a dive it experiences a g-force of more than one, how much more depends upon how fast it is flying and how quickly it is pulling out. If the g-force is high the blood may go to your feet and you might black out as your brain is starved of blood: pilots of high performance military aircraft wear special g-suits to prevent this. If the aircraft is going over the top of a loop (a bunt) the g-force will be less than 1, it could even be zero or negative. Negative g-force can lead to red-out where blood goes to your brain, and this is very dangerous. Pilots of military aircraft get round this problem by turning the aircraft over and flying upside down so that they experience positive rather than negative g - you might have noticed this when high-performance aircraft give displays at Air Shows.
If you fly in a much more ordinary aeroplane in a very carefully controlled trajectory at a very carefully controlled speed you may be able to achieve several minutes of zero g. Stephen Hawking would never have been allowed to go to the ISS but in 2007 he did experience zero g for four minutes in an aeroplane - a web search on Stephen Hawking + zero g will give you some nice videos.
© Barry Gray April 2020 | 0.843267 | 3.100409 |
A Nasa probe that explored Jupiter’s moon Europa, flew through a giant plume of water vapour that erupted from the icy surface and reached a hundred miles high, according to the latest data provided by the spacecraft. This recent discovery has further cemented multiple theories suggesting the potential presence of alien life on one of Jupiter’s moons. Some scientists believe that the Jovian moon, one of four first spotted by the Italian astronomer Galileo Galilei in 1610, is the most probably place to consider, in the hunt for alien life.
Nasa’s Galileo spacecraft spent eight years in orbit around Jupiter and made its closest pass over Europa on 16 December 1997. Europa was recorded to be nearly the same size as the moon that orbit’s Earth. As the probe dropped beneath an altitude of 250 miles, its sensors twitched with peculiar signals that scientists were unable to decipher at the time.Researchers now report in a new study that NASA’s Galileo Jupiter probe, which orbited the planet from 1995 to 2003, also detected a likely Europa plume during its flight in 1997. Scientists concluded that a sudden blast of water from the Jovian moon explained the Galileo probe’s odd measurements. They also suggested that the grainy images broadcasted by the Hubble Space telescope in 2016 showed plumes of water blasting from Europa’s surface.
The newly analyzed Galileo data provides “compelling independent evidence that there seems to be a plume on Europa,” said study lead author Xianzhe Jia, an associate professor in the Department of Climate and Space Sciences and Engineering at the University of Michigan.
On its closest flight, the probe sailed over Europa at more than 2,230 meters per hour. As it swept past, the instruments onboard reported a brief and sharp twist in the magnetic field and a rapid increase in the density of plasma (ionized gas) the spacecraft was flying through. Computer simulations created by Xianzhe Jia showed that a 120-mile-high geyser erupting from a relatively warm patch on Europa would project the same readings.“Our detection of a plume based on the Galileo data certainly strengthens the case for future exploration of Europa,” Jia said. A subsequent mission called Europa Clipper is scheduled to launch in 2020 with the hopes of exploring the potential existence or sustainability of life on Europa. Another mission, Esa’s Jupiter Icy Moons Explorer, or Juice, is expected to launch around the same time and explore Europa and two other Jovian moons, Ganymede and Callisto.
However, scientific discoveries can only materialize theories to a certain extent. The moons are hardly habitable housing an excruciating surface temperature that doesn’t rise above -160 C (-256 F). Existence of life at the moment seems only probable through the heat generated from tidal kneading driven by the massive gravitational forces that come with an orbit around Jupiter. Life may be thriving around hydrothermal vents at the bottom of the ocean in a world of frigid, eternal night.“Europa is completely engulfed by this saline ocean which lies beneath a crust of ice, and in terms of a places to host extant life, I think it’s the best location that we’ve got beyond planet Earth. It would be good to find out what is really there.” said William Sparks, an astronomer at the Space Telescope Science Institute in Baltimore.
In a relentless search for life beyond our planet, this may be our best bet. With endless possibilities in an infinite universe, the most impossible conditions may be the home to fascinating alien forms with different biological constructions. For all we know, we might discover forms that defy life as we know it and we can be assured that science is getting us there by the day!
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We regularly consider asteroids and comets as distinct kinds of small our bodies, however astronomers have found an rising variety of “crossovers.” These objects initially seem like asteroids, and later develop exercise, similar to tails, which can be typical of comets.
Now, the College of Hawai’i Asteroid Terrestrial-impact Final Alert System (ATLAS) has found the primary recognized Jupiter Trojan asteroid to have sprouted a comet-like tail. ATLAS is a NASA-funded undertaking utilizing wide-field telescopes to quickly scan the sky for asteroids which may pose an influence menace to Earth. However by looking out many of the sky each two nights, ATLAS typically finds different kinds of objects — objects that are not harmful, however are very attention-grabbing.
Early in June 2019, ATLAS reported what appeared to be a faint asteroid close to the orbit of Jupiter. The Minor Planet Middle designated the brand new discovery as 2019 LD2. Inspection of ATLAS pictures taken on June 10 by collaborators Alan Fitzsimmons and David Younger at Queen’s College Belfast revealed its possible cometary nature. Comply with-up observations by UH astronomer J.D. Armstrong and his scholar Sidney Moss on June 11 and 13 utilizing the Las Cumbres Observatory (LCO) international telescope community confirmed the cometary nature of this physique.
Later, in July 2019, new ATLAS pictures caught 2019 LD2 once more — now really wanting like a comet, with a faint tail manufactured from mud or gasoline. The asteroid handed behind the Solar and was not observable from the Earth in late 2019 and early 2020, however upon its reappearance within the evening sky in April of 2020, routine ATLAS observations confirmed that it nonetheless appears to be like like a comet. These observations confirmed that 2019 LD2 has in all probability been repeatedly energetic for nearly a yr.
Whereas ATLAS has found greater than 40 comets, what makes this object extraordinary is its orbit. The early indication that it was an asteroid close to Jupiter’s orbit have now been confirmed by way of exact measurements from many alternative observatories. The truth is, 2019 LD2 is a particular sort of asteroid referred to as a Jupiter Trojan — and no object of this sort has ever earlier than been seen to spew out mud and gasoline like a comet.
Trojan asteroids observe the identical orbit as a planet, however keep both round 60 levels forward or 60 levels behind alongside the orbit. Earth has at the very least one Trojan asteroid, and Neptune has dozens. Jupiter has tons of of 1000’s. The Jupiter Trojan asteroids orbit the Solar in two large swarms, one swarm orbiting forward of the planet (the place 2019 LD2 was discovered) and one swarm orbiting behind it. The Trojan asteroids have been captured into these orbits by Jupiter’s sturdy gravity. What makes 2019 LD2 so attention-grabbing is that we expect most Jupiter Trojans had been captured billions of years in the past. Any floor ice that might vaporize to spew out gasoline and dirt ought to have accomplished so way back, leaving the objects quietly orbiting as asteroids — not behaving like comets.
“We’ve believed for many years that Trojan asteroids ought to have massive quantities of ice beneath their surfaces, however by no means had any proof till now. ATLAS has proven that the predictions of their icy nature could be appropriate” stated Fitzsimmons.
What might have made 2019 LD2 abruptly present cometary conduct? Perhaps Jupiter captured it solely lately from a extra distant orbit the place floor ice might nonetheless survive. Perhaps it lately suffered a landslide or an influence from one other asteroid, exposing ice that was once buried below layers of protecting rock. New observations to seek out out are being acquired and evaluated. What’s sure is that the Universe is stuffed with surprises — and surveys to protect the Earth from harmful asteroids typically make sudden discoveries of innocent however fascinating objects that may reveal extra about our Photo voltaic System’s historical past.
“Though the ATLAS system is designed to seek for harmful asteroids, ATLAS sees different uncommon phenomena in our photo voltaic system and past whereas scanning the sky,” stated ATLAS undertaking principal investigator Larry Denneau. “It is an actual bonus for ATLAS to make these sorts of discoveries.” | 0.869808 | 3.844875 |
One aspect of our solar system is that it is essentially a closed system. The stars are so widely separated that it would be rare for a stray asteroid or other object from beyond the Oort cloud to enter our solar system. This means that nearly all the rocky material orbiting the Sun now was also part of the solar system billions of years ago. This has a few consequences, one of which is the tendency for the solar system to lie in a plane.
With a closed system, certain things are constant and unchanging. In physics, we say they are conserved. One of these conserved things is known as angular momentum. In simple terms, angular momentum is a measure of the amount of rotation of a system, but in actuality it is a bit more complicated. Angular momentum not only works for rotating bodies such as the Earth rotating on its axis, but also for collections of objects moving in different directions. For example, each of the planets orbiting the Sun has an angular momentum about the Sun.
The orbits of all the planets don’t lie within a single plane, but they are relatively close. However, if you add the angular momenta of all the planets, (and all the asteroids, Kuiper belt, etc) you get a total angular momentum of the solar system. Most of this angular momentum is due to the large outer planets. Together they account for about 98% of the total angular momentum of the solar system.
This total angular momentum can be defined by a plane known as the invariable plane. It’s invariable because the total angular momentum of the solar system is constant. The orbits of individual planets can change due to gravitational interactions, but the invariable plane can’t change. If the Earth’s orbit shifts relative to the invariable plane due to a gravitational interaction with Jupiter, then Jupiter’s orbit must also shift. Individual planets can gain or lose angular momentum, but they do so by taking it from or giving it to other planets.
Conservation of momentum also explains why the solar system (and other rotating systems like galaxies) tend to be planar. Imagine an early solar system where all the different matter is moving around the proto-Sun in all directions. All this higgledy-piggledy motion, with everything from the largest proto-planet to the smallest dust grain, has some total angular momentum. In principle you could add up the angular momentum of every object in the early solar system, and the total would be defined by the invariable plane. As objects collide and merge, the angular momentum of the new object is equal to the sum of the originals. As more and more objects collide, the sum of the larger and larger objects will tend toward the total angular momentum of the system. So as the planets formed, they tended to form along the invariable plane of the solar system.
This doesn’t mean that everything will tend toward the same plane. There are, for example, comets that have an orbital plane radically different from the invariable plane. But if you take the average of all these comets, this average is close to the invariable plane. There is also the Oort cloud on the outer edge of our solar system, which is distributed evenly around the Sun, and not in a plane at all.
But for the main planets, the invariable plane marks the plane of angular momentum that was there when the solar system began. And through the physics of mutual interaction drew the planets close to it. | 0.807461 | 3.962667 |
By Corey S. Powell
On June 22, a SpaceX Falcon Heavy will thunder off the launch pad at Florida’s Kennedy Space Center. It’s a colossal rocket — 230 feet tall, more than 3 million pounds — but the launch is a big deal mainly because of a tiny spacecraft it will carry: a bread-loaf-sized device designed to propel itself by gossamer sails that capture the pressure of sunlight.
The craft, dubbed LightSail 2, could be a prelude to a new era of spaceflight in which spacecraft forgo the rocket motors they’ve relied on for decades and simply sail on sunshine.
After seven days in space, LightSail 2 will pop out of its container, extend four long booms, and deploy four sheets of mirror-like Mylar plastic into a 340-square-foot, square sail. Then comes the truly magical part.
Sunlight falling on those sails will exert a tiny force, no greater than the weight of a paperclip resting on the palm of your hand. On Earth, the force of sunlight is so slight that it’s unnoticeable, which is why most of us have no idea it even exists. In space, with no air to compete with, light pressure acts as a gentle but persistent wind, strong enough to move a spacecraft.
“This will be the first time navigating by light in Earth orbit,” says Bill Nye, CEO of The Planetary Society, the Pasadena-based nonprofit organization that developed and funded LightSail 2. “We hope to increase the orbital energy or altitude, and change the inclination of the orbit by tacking the spacecraft like a sailboat.”
From there, the possibilities are nearly limitless. With a solar sail, a spacecraft could keep going to the moon, to asteroids, to Jupiter — to anywhere the wind of light blows, using no fuel at all.
It’s not easy to catch a solar breeze
LightSail 2 is the 21st century realization of an old desire to tack through space the way mariners navigate the seas. Four centuries ago, the German astronomer Johannes Kepler noticed that the tails of comets always point away from the sun — and had an inspiration. “Provide ships or sails adapted to the heavenly breezes, and there will be some who will brave even that void,” he wrote to Galileo in 1608.
In the 1970s, a NASA engineer named Lou Freedman became convinced that solar sailing was actually a feasible technology. When he co-founded The Planetary Society in 1980, that idea became embedded in the group’s mission. But figuring out how to build an enormous, ultralightweight sail and get it into space on an affordable budget proved a stubborn challenge.
Cosmos-1, the society’s first attempt, launched in 2005 but was lost after the rocket carrying it aloft failed 82 seconds into flight. A scaled-down successor, LightSail 1, successfully deployed its sail in 2015. But it was just a technology demonstrator placed in a low orbit, where the drag from Earth’s upper atmosphere overwhelmed the delicate push from the sun.
Other would-be space sailors have quietly made their own attempts, with similarly mixed results.
A 2015 test mission called CubeSail, built by the Surrey Space Centre in the U.K., failed to deploy properly, the Centre’s director, Guglielmo Aglietti, told NBC News MACH in an email. Over the past decade, three other small sail missions — NASA’s NanoSail-D, Canada’s CanX-7 and Surrey’s InflateSail — did work. But like LightSail 1, they operated close to Earth, where their sails acted like drag chutes rather than majestic celestial riggings.
Once more, into the wind
By far the greatest triumph in solar sailing so far has come from Japan’s IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun), launched into orbit around the sun in 2010. Once in deep space, the craft spun open a 46-foot-wide square sail and, for the first time in history, began steering and changing its speed by harnessing sunshine.
“It was one of the most moving moments in my life,” Yuichi Tsuda of the Japan Aerospace Exploration Agency (JAXA) told MACH in an email.
Over the next three years, IKAROS measured the acceleration due to light pressure and tested ways to control its motion using liquid crystals in the sail (similar to an LCD electronic display) that could make it more or less reflective.
“We fulfilled all our goals perfectly,” Tsuda said, reporting that the craft had been able to adjust both its course and its orientation by navigating into the wind of sunshine. Contact with IKAROS ended as expected in 2015, he added, but the spacecraft continues to loop around the sun between Earth and Venus, “its orbital shape changing and changing due to the light pressure.”
In parallel with those successes, though, IKAROS revealed how much work remains to be done to realize the full potential of light propulsion. Its sail was not nearly big enough for serious swooping through the solar system, taking a full year on average to boost or reduce its speed by one half of 1 percent. IKAROS was therefore designed as a hybrid, augmenting light pressure with more conventional thrusters powered by electricity-generating solar cells built into the sail.
Sailing goes mainstream
LightSail 2 is intended to help resolve the technical problems and turn light sails into a reliable, low-cost, zero-propellant way of getting around in space. Nye takes inspiration from test pilot Tex Johnston, who in 1955 proved the flightworthiness of Boeing’s 707 prototype by doing a crazy midflight roll in front of the press corps. “He supposedly told the press, ‘One test is worth a thousand expert opinions.’ That’s why we’re flying this,” Nye says.
A team at CU Aerospace, a private company affiliated with the University of Illinois at Urbana-Champaign, has embraced the same daredevil spirit. Last December they launched a pair of satellites called CubeSail (unrelated to the British experiment of the same name) into Earth orbit. When they reach their target location in mid-2020, the two will separate and unspool an 800-foot-long ribbon between them — a totally new kind of solar sail.
NASA is in the game, too, with a solar-sailing mission called Near Earth Asteroid Scout. It will fly aboard the agency’s long-delayed Space Launch System rocket “whenever it launches,” says mission principal investigator Les Johnson of NASA’s Marshall Space Flight Center in Huntsville, Alabama. That could happen right around the time of the CubeSail test run.
The plan for NEA Scout is to one-up IKAROS by using the sail to reach a specific target and perform a detailed reconnaissance for the first time. “Our technology goal is to demonstrate the ability of a solar sail to propel and navigate a spacecraft through space,” Johnson says. “Our science goal is to take photos of and characterize a near-earth asteroid.”
If these missions succeed as expected, light sailing could finally begin to take off. The limited pressure of sunshine means sail-powered craft will take a long time to reach their targets, but by dispensing with fuel, they could be very simple and cheap. The budget for LightSail 2, for instance, is $7 million, a tiny fraction of a typical NASA mission. And since sunshine never runs out, light sails can keep going pretty much forever. “All you need is patience. Once you are in orbit, you’re driving,” Nye said.
With that in mind, JAXA has plans in the works for an IKAROS successor called OKEANOS, which would sail its way out to a group of mysterious asteroids near Jupiter. Fleets of low-cost solar sails are another possibility. David Carroll, president of CU Aerospace, says CubeSail was conceived as a first step toward UltraSail, an enormous four-winged sailing craft that the company has been designing for years.
“The beauty of the UltraSail concept is the ability to tack the sails, allowing you to travel all over the solar system back and forth as desired without requiring any sort of refueling,” Carroll says. It could mark a transition from sailboat to tugboat, creating an interplanetary cargo network powered by nothing more than the relentless shining of the sun. | 0.883311 | 3.73152 |
“Some part of our being knows this is where we came from. We long to return. And we can. Because the cosmos is also within us. We’re made of star stuff. We are a way for the cosmos to know itself.”
—Carl Sagan, Cosmos
That Carl Sagan quote is among one of his most famous sayings, and for good reason: it expresses a joy, a connection between us and the cosmos that gives his famous television series its title. It’s (dare I say) a fact so romantic that Neil DeGrasse Tyson called it the most astounding piece of knowledge he would share about the universe.
It’s a stirring thought: nearly every atom of our bodies passed through a star, and many were forged by stars as well. That’s also true for the rocks under our feet, the gases filling our lightbulbs, the air we breathe, even labradoodles. Our galaxy contains billions of planets, both wanderers and homebodies, and it’s a near-certainty that the Milky Way isn’t unique in that regard. Each one of those planets, whether life-bearing or not, is made of star stuff. It’s even more amazing when you consider that much of the “normal” stuff of Earthly life—carbon, oxygen, nitrogen, iron, calcium, sulfur, and so forth—comprises about 1% of all atoms in the universe.
We are common; we are rare.
The story of the atoms in our bodies is the story of the universe in a real sense. A proton in the nucleus of an iron atom in a red blood cell may have been born in the Big Bang, passed through several stars, and been flung across the galaxy before ending up at its current place in your anatomy.
Most of the atoms in the cosmos are hydrogen—the simplest atom, whose just a single proton for a nucleus—while most of the rest are helium, the next-smallest atom. Most of those atoms (along with small amounts of lithium and boron) were born in the intense few minutes following the Big Bang. Despite the intense heat and pressure, there simply wasn’t time to create many heavier nuclei. The early universe was chemically simple.. When the unvierse’s first generation of stars coalesced, they were mostly made of single electrons and protons (that is, hydrogen), since that’s what was available. According to our models, however, these stars were huge, so they quickly fused their available hydrogen into helium, and were correspondingly short-lived. Once the hydrogen supply in its core is exhausted, a star undergoes a series of end-life expansions and contractions, with new fusion processes forging carbon, oxygen, and—if the star is sufficiently massive—heavier elements. (Our Sun is smack in the middle of the main part of its life, about 5 billion years from running out of hydrogen fuel.)
For the early, huge stars in the universe, their lives ended abruptly in supernova explosions, which are hot and energetic enough to produce new elements on their own, providing both a destructive and creative environment in one place. Even as they tear the star apart, the explosions create and fling new chemical elements out into space. The first stars may have been born of hydrogen, but they died in a cloud of heavier atoms. These new elements were still not numerous compared to the primordial hydrogen and helium, but even their small numbers were sufficient to begin changing the chemistry of the cosmos.
The chemistry of life also began here. Hydrogen was born in aftermath of the Big Bang, but without the oxygen from stars, there could be no water. Your body is mostly made of water (though how much percentage-wise depends on how you calculate it), and all life as we know it depends on liquid water. The hydrogen in that water passed through a star to join with the star-made oxygen, to become part of the cytoplasm in a skin cell of your epidermis billions of years later.
The second generation of stars formed out of the debris of the first, and not all of these were huge and fast-burning; many are still around today. Those that were massive, however, had similarly short lifetimes, and also died in supernovas, distributing yet more elements out into space. The iron in the hemoglobin in your blood was made in such an explosion.
Supernovas are not the only way dying stars spread the chemical wealth around. The atmospheres of huge dying stars are only tenuously bound by gravity. As they pulsate, they shed huge amounts of gas in the form of stellar wind. (The analog for the Sun is the solar wind, which thanks to our star’s quieter life is a lot calmer.) The cooler environment away from the star allows the atoms to come together to form molecules: methane and carbon dioxide, some of the precursors of life.
Betelgeuse—the bright red star forming the “shoulder” of the constellation Orion—is one such dying giant. Observations using the Very Large Telescope (VLT) in Chile discovered that Betelgeuse is surrounded by a huge cloud of ejected material, nearly 2 billion kilometers across. The cloud contains a wealth of oxygen-rich molecules, especially silicon dioxide—which on Earth is common beach sand. An atom of silicon in your own aorta was swept into space by stellar winds.
Outside of stars’ cores are their envelopes, which are too cold to fuse atoms, yet act as a different kinds of nuclear reactors. Neutrons from the core bombard atoms in the star’s outer layers, creating heavier elements that are carried away by stellar wind. Even the rare element technetium, which is unstable and not naturally occurring on Earth (its name even means “artificial”), is produced in the envelopes of giant stars. Some of the calcium in your teeth and the milk you give to nurse your baby was also forged this way.
Even lower-mass stars, which don’t die explosively, shed their outer layers gently in the form of planetary nebulas, seeding space with elements and organic molecules, including amino acids, the building blocks of proteins found in you and every other organism. Other kinds of stellar death—the explosion of a white dwarf and the collision of pulsars—could also be responsible for some atoms.
The Sun, with its planets and beings who sit around thinking about this stuff, is neither a first- nor second-generation star. Our solar system formed from a nebula that was itself the graveyard of at least one star, which contained enough iron and nickel to make Earth, the Moon, and the other rocky worlds. In fact, researchers have identified two grains of silicon dioxide in meteorites—almost unimaginably small samples—containing isotopes of oxygen that aren’t known to form from stellar atmospheres, but match those produced in supernovas.
Whatever the specific source, between fusion and other nuclear processes in dying stars, with winds and explosions to disperse their products, stars provide nearly every element found on Earth and the means to bring them into space. The tale of these atoms and their journey from the beginning of time to our anatomy is our backstory. Even better, it’s a story we share with labradoodles and meteorites, stones and running brooks. I would not change it a bit.
Matthew Francis is a physicist, science writer, public speaker, educator, and frequent wearer of jaunty hats. He’s currently writing a book on cosmology, with the working title, Back Roads, Dark Skies: A Cosmological Journey. | 0.881309 | 3.722668 |
Sensors are usually thought of in terms of physical devices that receive and respond to electromagnetic signals – from everyday sensors in our smartphones and connected home appliances to more advanced sensors in buildings, cars, airplanes and spacecraft.
No physical sensor or aggregation of electronic sensors, however, can continuously and globally detect disturbances that take place on or above the earth’s surface. But the physical atmosphere itself may offer such a sensing capability, if it can be understood and tapped into.
To that end, DARPA recently announced its Atmosphere as a Sensor (AtmoSense) program, whose goal is to understand the fundamentals of energy propagation from the ground to the ionosphere to determine if the atmosphere can be used as a sensor. A Proposers Day is scheduled for February 14, 2020, in Arlington, Virginia.
It’s well known that energy propagates from the Earth’s surface to the ionosphere, but the specifics of how that happens is not currently known enough to use the atmosphere as a sensor. Scientific literature has clearly documented that events like thunderstorms, tornadoes, volcanos, and tsunamis make big “three-dimensional wakes” that propagate to the upper reaches of the ionosphere and leave a mark there.
Since that energy traverses several other layers of atmosphere – the troposphere, stratosphere, and mesosphere – on its way up to the ionosphere, the idea is to try and identify the disturbances the “wake” is making along its way to see if researchers can capture information to indicate what type of event caused it.
“Maybe I don’t have to directly observe events like an earthquake or tsunami,” said Air Force Major C. David Lewis who is the AtmoSense program manager in DARPA’s Defense Sciences Office.
“Perhaps I can learn what occurred from information in the atmosphere. I want to find out how much information is available, and if I can disaggregate the signal I’m interested in from other natural phenomena creating noise in the background.”
The AtmoSense program seeks proposers from the atmospheric science community, who have extensive experience in atmospheric modeling and simulation. Also of interest are experts offering very unique ways to measure atmospheric properties, such as the basic PV=nRT variables – pressure, volume, density, temperature, or derivatives of such. Beyond these basic atmospheric variables, the mesosphere and lower ionosphere provide electromagnetic opportunities for measurement due to their charged nature.
“We typically model, simulate, and measure properties in the troposphere, which is where terrestrial weather happens,” Lewis said.
“But we don’t really make those measurements in the stratosphere or the mesosphere, or the bottom part of the ionosphere, because no one has really been keenly interested in it and it’s hard to get up there. Sometimes the mesosphere is even called the ‘ignorosphere,’ but we know that information traverses it, so we’re really looking for scientists and engineers with unique ways of potentially measuring different aspects of the atmosphere.”
Another key area for the program is measuring and understanding background noise that weakens or destroys signals of interest.
“When we think about the possible background entropy, there are jet streams, compression of the fluid, shear forces, Coriolis forces, etc.; all those things trigger some sort of turbulence that destroys information,” Lewis said.
“When it comes to geophysical and meteorological sources of atmospheric disturbance there’s a frequency spectrum emitted from infrasound all the way up to the ultrasound. Some of those frequencies are more immune to atmospheric entropy than others, and those are what we’d like to capture.”
The program calls for two phases. The first phase is concept development (27 months), and the second phase is proof of principle field testing (12 months). If successful, AtmoSense could enable new ways in the future to identify and give insight into events such as earthquakes, tsunamis, storms, tornados, and asteroid activity. | 0.834885 | 3.191005 |
Estimating sizes and distances on planetary surfaces is a difficult task on spacecraft imagery because of the lack of familiar landmarks of known sizes, the ubiquity of scale-independent landforms (craters, cracks, cones, dunes), and also due to the different radius of planets and satellites.
To estimate the extent of features and distinct regions is therefore almost impossible on a planetary surface without a scale. A map that the student is familiar with greatly helps estimating sizes and distances since it projects the known environment onto the planetary surface, virtually placing the student into a known 3D environment. The basic goal, however, is not just to add a sense of sizes to a map view, but to help the virtual exploration in the environment of another planetary surface. Ultimately, by exploring a lifeless planet in imagination with a sense of the real scale, the unique characteristics of our own, well-accustomed terrestrial environments will be emphasized.
A few unusual phenomena that will likely be encountered in viewing orbital images or planetary maps are: the inability to discriminate sizes of simple craters and the abundance of craters; problems in viewing craters and hills in inverted relief, the large sizes of canyons, troughs, volcanoes, lava flows; the large sizes of terrains with undifferentiated (similar, or repetitive) relief features in general (without vegetation and man-made features that would otherwise segment an undifferentiated geologic substrate).
Students should also focus to deliminate single features by identifying boundaries where a terrain changes. These are the contact lines of geologic units or features, and even think about their origin, stratigraphic relations (which was produced first, and which cut into that or covered that subsequently) or relief changes. This is a basic requirement to be able to identify and discriminate standalone “features” on the landscape.
How the App works
The outline of a chosen country, U.S. state or a standard 100 km radius Mars Exploration Zone can be displayed and moved on the surface of another planet or moon (currently, Mars, Venus, the Moon, Io, Titan and Jupiter), keeping its original size. This comparison can be done either on the surface of a rotatable globe model or on a 2D map in Web Mercator projection.
Select and display maps: The user can select thematic raster maps from eight planetary bodies. Scale and legend is included in the maps in rasterized form.
- Zoom in-out: mouse scrolling or +/- button on screen
- Position of the globe within the screen: Shift+drag mouse
- Rotate globe: drag mouse
- Change center of perspective: ctrs+shift+drag mouse
- Start/end line measurement: mouse click
- Reset distance measurement tool: turn the tool off and on
**Country overlay: The user can overlay the vector outline of any country or U.S. State or a standard 100-km-radius Exploration Zone on any embedded planetary body. The outline can be displayed and moved on the surface, keeping its original size, in both 2D and 3D views. When drawing the country outlines, the radius differences of the bodies are taken in account.
Projection: The maps have two views: a 2D flat map in Web Mercator projection, and a 3D rotatable virtual globe model (no surface relief is shown in 3D). These two different view modes offer various uses. The flat version can also be used to demonstrate the high area distortions of the Mercator projection e.g. by moving Greenland to lower latitudes (Fig. 3). However, due to the properties of Mercator projection (poles are projected to infinite distance), polar regions cannot be explored effectively in the flat view, only on the 3D globe.
The virtual globe mode is a useful tool to demonstrate the size differences of the planetary bodies. For instance, Australia on the Moon would cover almost an entire hemisphere (Fig. 4).
Distance measurement: This tool is used to draw a polyline, calculates and displays distance and travel time between the two end points, in various units that includes the maximum speed of a walking astronaut, an automatic rover, a human-driven rover and a car on a blacktop freeway.
Coordinate display: It shows the position (IAU geographic coordinate) of the cursor. Earth and Moon coordinates are displayed in the ±180 longitude system, Mars and Venus in the 0-360° Eastern longitudes system and the other bodies in the 0-360° Western longitudes system.
Colors: The user can determine the color of the measurement polyline and the country outline.
Screenshot: Using the screenshot feature built into the App, users can save the current view as a png image file that includes any traverses the user created but excludes the user interface), providing a printable background map for further activities. The user can continue working on this map in an external image processing application where they can add settlements, roads, regions of scientific interests etc., learning the concepts of planetary physical geography, toponymy, cartography, mission and city planning. These aspects are discussed in Chapter 4 in detail.
Place names: Place names are rasterized or “burnt into pixels”, so that we could use the full spectrum fonts can provide, including font faces, sizes and styles, to distinguish places of different type, size and landscape hierarchy level. This function is not available in nomenclature vector layers that are not feature polygon-linked, as is the case for the majority of planetary map platforms. The major disadvantage of the rasterized nomenclature, however, is that it is not scale-dependent: by zooming into the view, the names become disproportionally large and place names cannot be searched for.
Info (about): This window contains information on the Tool, including links to references and online tutorials.
The Mercury globe is a green-to-red color hillshade MESSENGER Global DEM topographic map. Mercury is characterized by densely cratered terrains and less cratered smooth volcanic plains. Some large basins resemble those on the Moon. Wrinkle ridges (long ridges) occur in all parts of the planet, likely resulted from the cooling of the crust.
The Venus view is a monochromatic colorized mosaic of Magellan radar images in which bright tones show rough areas (trough systems, tectonically deformed tesserae, and lava flows), medium tones show lava plains, and dark tones represent smooth, dust covered regions.
The Moon topographic map is based on the Lunar Reconnaissance Orbiter Camera Wide Angle Camera (LROC WAC) DEM data. The Moon is a relatively small body, with two distinct terrains colored according to their different altitude range blue and yellow: lowland plains (maria) and highlands, respectively. This topographic difference coincides with the albedo difference visible to the naked eye: volcanic (basaltic) maria are dark and megabreccia-dominated anorthositic highlands are bright. This difference is partly due to the different materials and the different roughness of the two terrain types: basalt is darker and these plains are also smoother, while anorthosite is brighter and highlands are also densely cratered. Prominent features of the map are the rings of multiring basins usually with a mare plain at their centers. The enormous, ancient South Pole-Aitken Basin is also evident in the relief map but remains hidden in the photomosaic view.
Mars has two views: one topographic and one albedo. The topographic color hillshade map of Mars is based on MOLA gridded DEM and displays the lowlands and basins in white to yellow, highlands in brown, high shield volcanoes in dark brown. The albedo globe shows the permanent, bright ice caps, medium-toned dust covered regions and dust-free dark areas that may be covered with basaltic sand. The albedo map is produced from the Mars Global Surveyor Mars Orbiter Camera (MGS MOC) photomosaic and shows both albedo and topographic place names.
The map of Io is a false color Galileo–Voyager photomosaic in which the most distinct features are the red, sulfur-rich plume deposits of active volcanic centers (symbolized by red asterisks) and dark lava-filled calderas. The yellow coloration of the surface is caused by sulfur coating while the brightest areas are covered by a volatile, sulfur dioxide frost, deposited from volcanic degassing. Most irregular patterns represent lava flows, while the over 100 mountain blocks are most apparent in the south polar region where they are shown casting long shadows in this mosaic. Mountain peaks are indicated by black triangles and peak heights are displayed in meters. These symbols are taken from terrestrial maps and are not usual parts of planetary maps.
The map of Jupiter shows the cloud bands with nomenclature, in which any country can be easily placed into the white ovals and the Great Red Spot. The map background is the color image of Jupiter produced by the Hubble Space Telescope OPAL Program. Since Jupiter has no solid surface, this map only shows the size of the planet and its atmospheric features (clouds, cyclones) relative to others. NOT SUITABLE FOR LANDING – NO SOLID SURFACE.
The composite (infrared+radar) Titan globe shows the Cassini infrared (ISS) view of the satellite that shows dark equatorial dunes, dark polar liquid methane filled lakes and bright terrains made of rocks of H2O ice. Stripes of Cassini radar images give a higher resolution view in the north polar regions.
In addition to the above listed maps, Google’s photomosaics of Mars (THEMIS daytime thermal infrared mosaic at 100 m/px raster data resolution) and the Moon (Clementine albedo mosaic, 100 m/px resolution) are also embedded into the App without any modification, and provide the highest resolution background maps.
The maps have somewhat different themes. This difference is partly due to the differences in planetary mission designs, instruments and surface conditions: for instance, the atmosphere of Venus and Titan is opaque in visible wavelength and therefore an optical image mosaic of the surface is not available for this body.
Photomosaic maps show the surface at a particular wavelength(s)and solar incidence angle. Low-sun mosaics are composed of images taken when the Sun is near the horizon. These images emphasize relief by showing long shadows. High-sun images show albedo, or reflectivity, of the surface that may represent differing composition, grain size, or surface roughness. Albedo features may or may not correspond to topographic features (relief). These maps are usually monochromatic (greyscale), and may show the surface in visible, near infrared or thermal infrared wavelengths. Mosaics of images taken at different wavelengths may be combined into a color image. These are usually false color mosaics and include visible and infrared bands. Examples: Mars, Moon, Io
Imaging radar maps show the radar reflectance properties of the planetary surface. A radar instrument onboard the orbiting spacecraft “illuminates” the surface by cm-scale radar pulses emitted by the spacecraft’s transmitter. A portion of this electromagnetic radiation is reflected from the surface and is received by the antenna the radar instrument. The radar echo or radar return depends on the roughness of the surface relative to the radar wavelength used for the mapping. Typically, dusty or sandy (particles less than a centimeter) areas do not reflect cm-scale radar waves and remain dark and rocky surfaces (particles greater than a cm) produce strong radar return signal and are represented as bright areas on radar maps. Radar maps are typically displayed in monochromatic (greyscale) form. Examples: Venus, Titan (partially).
Topographic maps show surface elevation and relief. Although the initial topographic dataset (digital elevation model, DEM) has no associated colors and could be displayed in greyscale shades, these maps are typically displayed in a custom-made color ramp (color coding) combined with hill-shading that enhance the sense of relief. This visualization provides the most familiar cartographic picture of a surface. The color ramp for topographic maps of different bodies could be similar, however, we chose different color ramps to reflect a color-related mental association of the particular body. These colors are symbolic and do not correspond to the real color of the body, neither follow the color ramp of terrestrial physical geographic maps where colors are related to the presence of water or are symbolic, simplified representations of zonal vegetation. Students should familiarize with the color ramp before studying the map (rasterized legends are available in the maps). Planetary topographic data may be obtained from radar altimetry, laser altimetry or stereo imaging etc., techniques. Examples: Mercury, Mars, Moon.
Merged themes. A map product may combine different themes. Relief can be shown by colors or shadows (either in a low-sun photomosaic or by producing hillshading from a digital elevation model). Surface material / compositional units may be emphasized in albedo maps, high-sun (local noon) or nighttime infrared photomosaics taken when shadows are equally absent. While noon images show the reflectance of surface materials, nighttime thermal infrared images show thermal inertia properties. | 0.905024 | 3.906114 |
User:Robertinventor/Old/Modern Mars Habitability/Old revision from Wikipedia with extra quotes
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One of the central questions of modern Astrobiology is whether there is, or ever has been life on Mars. Mars probably had oceans in the past, and it definitely had lakes and a thicker atmosphere. Modern Mars has become cold, dry, and almost uninhabitable, yet, if life did ever arise on Mars, some hardy microbes and perhaps even multicellular life might survive there right through to the present. The only missions to search for life on Mars, the two Viking missions, returned results that were inconclusive. However the instruments were not designed to cope with the unusual conditions which Viking discovered on Mars, which may have confused the results of the experiments. Also, they didn't know enough about Mars at that time to target the regions we now think are most likely to have present day life.
Life would meet many challenges on present day Mars. Liquid water boils at 0 °C, over much of its surface. Even at the depths of the Hellas basin, any water is close to its boiling point of 10 °C and will dry out quickly. Ice also evaporates into the atmosphere over geological timescales - and most of the equatorial regions are thought to be dry to depths of tens of meters. As its axial tilt varies, Mars atmosphere is sometimes thicker, and liquid water may then form on the surface - but any dormant life in the top few meters of soil would be destroyed over periods of millions of years by cosmic radiation.
However, in 2008, droplets were observed on the landing legs of Phoenix. Sadly, there was no way to analyse them, but the leading hypothesis is that they were droplets of salty water. Phoenix also made isotopic measurements which show that the Mars atmosphere has exchanged oxygen molecules with liquid on the surface in the recent geological past. This could indicate either recent episodic occurrences of liquid water (for instance after a meteorite strike) or water present every year, in contact with the atmosphere.
We now know of many seasonal changes in the surface of Mars which are only visible in high resolution photographs. Most of these are now thought to be caused by dry ice or wind effects. However, the "Recurrent slope lineae", and some of the "flow like features" form in conditions that suggest the occasional presence of small quantities of water on Mars. The evidence of flowing brines in the RSLs is strong, though it's not known if they are habitable. Curiosity has also found indirect evidence of a brine layer 15 cm below the sands that it drives over, though most scientists think that this layer is not habitable for Earth life. Recent Mars surface simulations by Nilton Renno and his team have shown that small droplets of water can form on salt / ice interfaces for a few hours per day almost anywhere on the surface of Mars, and this may explain the Phoenix leg droplets observations.
In a separate development, research by the German aerospace company DLR in Mars simulation chambers and on the ISS show that some Earth life can survive simulated Mars surface conditions without any water at all, and photosynthesize and metabolize, slowly. It can do this using the high relative humidity of the Mars atmosphere at night. All of this work was done after the Phoenix discoveries in 2008.
Other potential habitats include lakes formed in the higher latitudes after cometary or meteorite impacts, or as a result of volcanism. Covered by ice, these may remain liquid for centuries, or up to a few thousand years for the largest impacts. The planet may also have underground trapped layers of water heated by geothermal hotspots. Also there are suggestions that Mars may have a deep hydrosphere, a liquid layer below its cryosphere, a few kilometers below the surface. Deep rock habitats on Earth are inhabited by life so if this layer exists, it may also be habitable on Mars.
The main questions are
- Do any of these potential habitats exist?
- Are they habitable? For instance, liquid water, if present, could be too cold, or too salty for Earth life
- Are they in fact inhabited by any forms of life? As Mars is so inhospitable, life might not be able to spread to new habitats easily. So there might be life in some of the habitats and not in others. Or life on Mars may have gone extinct, or never evolved at all, in which case none of the habitats would be inhabited.
These discoveries have renewed interest in this topic, for both deep subsurface life and more controversially, for surface or near surface life. Although many present day astrobiologists say that the surface is likely to be sterile of life, others treat it it is an open question whether it has life, either in temporary habitats recolonized from below,, or continuously on or near the surface. Others say that their experiments show that some parts of the surface of Mars are likely to be habitable for some lichens and cyanobacteria, taking advantage of the night time humidity, and a small minority of authors say that in their view, their reanalysis of the Viking Labeled Release experiments suggests a strong possibility that present day life has already been detected on present day Mars. The first conference on the Present Day Habitability of Mars was held in 2013 in UCLA. The 2017 conference session on Modern Mars Habitability ran from April 24–28 in Mesa, Arizona
- 1 Viking observations - did Levin's labeled release experiment find life?
- 2 Phoenix observations
- 3 Methane plume observations by Curiosity and from Earth
- 4 Dry Gullies
- 5 Warm Seasonal flows (Recurrent Slope Lineae)
- 6 Sun warmed dust grains embedded in ice
- 7 Flow like features
- 8 Life able to take up water from the 100% night time humidity of the Mars atmosphere
- 9 Deliquescing salts taking up moisture from the Mars atmosphere
- 9.1 Eutectic and eutonic mixtures, e.g. of chlorides and perchlorates deliquesce at a lower relative humidity, and remain liquid at a lower temperature than either separately
- 9.2 After salt mixtures take up water, they retain it after supercooling, and reduced humidity
- 9.3 Effects of micropores in salt pillars
- 9.4 Implications of these effects
- 9.5 Challenges for life in these liquid layers of deliquescing salts
- 9.6 Curiosity observations - indirect evidence of deliquescing salts in equatorial regions
- 10 Advancing sand dunes bioreactor
- 11 Droplets of liquid water on salt / ice interfaces
- 12 Shallow interfacial layers a few molecules thick
- 13 Ice covered lakes that form in polar regions after large impacts
- 14 Temporary lakes resulting from volcanic activity
- 15 Possibility of geological hot spots in present day Mars
- 16 Potential for cave habitats on Mars
- 17 Sub surface ice sheets in the equatorial regions
- 18 Hydrosphere - possible layer of liquid water several kilometers below the surface
- 19 Habitability factors for life on Mars
- 20 Lowest temperature for life on Mars
- 21 Lowest water activity level for life on Mars
- 22 Challenge of ionizing radiation
- 23 Views on the possibility of present day life on or near the surface
- 24 Plausible microbial metabolisms for present day Mars
- 25 Candidate lifeforms for Mars
- 26 Expose R2 test of candidate lifeforms for Mars on exterior of ISS
- 27 Uninhabited habitats
- 28 Search for a second genesis of life on Mars
- 29 Planetary protection issues
- 30 Follow the nitrogen
- 31 Planned and proposed missions to search for present day life on Mars
- 32 Instruments designed to search for present day life on Mars "in situ"
- 33 See also
- 34 External links
- 35 References
Viking observations - did Levin's labeled release experiment find life?[edit source | hide | hide all]
The Viking landers (operating on Mars from 1976-1982), are the only spacecraft so far to search directly for life on Mars. They landed in the equatorial regions of Mars. With our modern understanding of Mars, this would be a surprising location to find life, as the soil there is thought to be completely ice free to a depth of at least hundred meters, and possibly for a kilometer or more. It is not totally impossible though, as some scientists have suggested ways that life could exist even in such arid conditions, using the night time humidity of the atmosphere, and possibly in some way utilizing the frosts that form frequently in the mornings in equatorial regions.
The Viking results were intriguing, and inconclusive. There has been much debate since then between a small number of scientists who think that the Viking missions did detect life, and the majority of scientists who think that it did not.
The Viking lander had three main biological experiments, but only one of these experiments produced positive results.
- The Gas Chromatograph/Mass Spectrometer searched for organics, and found no trace of them.
- The Gas Exchange experiment searched for any gases that evolved from a sample of the Mars soil left in a nutrient solution in simulated martian atmosphere for twelve days. This experiment did detect gases, but so did the control, which repeated the experiment with a sample heated to sterilize it of any possible life. This suggests a chemical explanation.
- The labeled release experiment used nutrients tagged with 14C. It then monitored the air above the experiment for radioactive 14CO2 gas as evidence that the nutrients had been taken up by micro-organisms. This experiment produced positive results. Also, in this case, the control experiments came out negative. Normally this would suggest a biological explanation. For this experiment the microbes don't have to grow, reproduce. They just have to metabolize the organics and produce the 14CO2 gas in the process.
The conclusion at the time, for most scientists, was that the Labeled release experiment had to have some non biological explanation involving the unusual chemistry on Mars. One idea put forward by Albert Yen of JPL was that first carbon dioxide could react with the soil to produce superoxides in the cold dry conditions with UV radiation, which could then react with the small organics of the LR experiment to produce carbon dioxide. The other two experiments seemed to rule out any possibility of a biological explanation.
Some of the LR data remained hard to explain as chemistry and the experimenter's Principle Investigator Gilbert Levin maintained from the beginning that his experiment probably detected life. Here are some of the things that any theory has to explain, in addition to the non detection of organics by the other instruments:
- The LR response produced a lot of carbon dioxide rapidly, which some criticized as "too much too soon" for the levels of life expected there.
- A second injection of nutrient actually lead to a 20% decrease in the previously evolved 14CO2
- A sample maintained at 10 °C in darkness for two months at one site and three months at another had no response to the nutrient
- A sample heated to 46 °C produced 60% less gas
- A sample heated to 51 °C became erratic and produced 90% less gas
His comments on how this could be explained biologically are that first, the amount of 14CO2 released is comparable to a sample from Antarctica and less than is usually released in tests on Earth. The second injection seems to have just wetted the sample and lead to absorption of 14CO2 and his conclusion is that the life died during the experiment, which is not too surprising given that most microbes even on Earth can't be cultivated in the laboratory. The difference in effect between 46 °C and 51 °C he considers to be strongly suggestive of life and hard to explain chemically for such a small change. The results for the samples kept in darkness he also considers to be hard to explain without biology.
First, some have suggested that the gas chromatograph may not have been sensitive enough to detect the organics. Though other scientists have suggested that they could have detected low levels of organics....
Then in 2002, Joseph Miller, a specialist in circadian rhythms thought he spotted these in the Viking data. He was able to get hold of the original Viking raw data (using printouts kept by Levin's co-researcher Pat Straat) and on re-analysis this seemed to confirm his conclusions.
- The data, though it follows temperature changes, is smoother than you'd expect from a purely chemical reaction response.
- It is also delayed by 2 hours. From analysis of the experiment he concluded that though a 20-minute delay could be explained using variability in CO2 solubility, 2 hours seems too much of a delay to explain that way.
- There are signs of a change of rhythm after the second nutrient injection.
- In an accidental experiment, one of the samples was kept for two months in cold and darkness before it was used. This showed no daily cycle. This is quite hard to explain on basis of chemistry.
On the other hand, a paper published in 2013 by Quinn has refined the chemical explanations suggested for the labeled release observations, using radiation damaged perchlorates. By simulating the radiation environment on Mars, he was able to duplicate radioactive 14CO2 emission from the sample.
In short, the findings are intriguing but there is no consensus yet on whether the correct interpretation is biological or chemical. Most scientists still favour the chemical explanation, though a few scientists have recently shown renewed interest in a possible biological explanation.
For a more detailed coverage see Viking lander biological experiments
Droplets on the Phoenix legs[edit source | hide]
Until 2008, most scientists thought that there was no possibility of liquid water on Mars for any length of time in the current conditions there. However, in 2008 through to 2009, droplets were observed on the landing legs of Phoenix.
Unfortunately, it wasn't equipped to analyse them but the leading theory is that these were droplets of salty water. They were observed to grow, merge, and then disappear, presumably as a result of falling off the legs.
These may have formed on mixtures of salt and ice that were thrown up onto its legs when it landed. Experiments by Nilton Renno's team in 2014 in Mars simulation chambers show that water can form droplets readily in Mars conditions on the interface between ice and calcium perchlorate salts. The droplets can form within minutes in Mars simulation conditions. This is the easiest way they have found to explain the observations.
Phoenix isotope evidence of liquid water on the Mars surface in the recent geological past[edit source | hide]
Phoenix also made isotopic measurements of the carbon and oxygen atoms in the atmospheric CO2 in the atmosphere. These measurements show that the oxygen has exchanged chemically with some liquid on the surface, probably water, in the recent geological past. This gives indirect but strong evidence that liquid water exists on the surface or has existed, in the very recent geological past.
In detail, first they found that the ratio of isotopes for 13C to 12C in the atmosphere is similar to Earth. Mars should be enriched in 13C because the lighter 12C is lost to space, but isn't. So this shows that the CO2 must be continually replenished. So Mars must be geologically active at least from time to time in the recent geological past.
Then with the oxygen, their findings were the other way around. The CO2 is enriched in 18O compared with the 16O compared with CO2 as emitted from volcanic activity. They can make this deduction using information from meteorites from Mars, one of which was formed as recently as 160 million years ago. This shows that the oxygen in the CO2 in the atmosphere must have reacted chemically with water on the surface in order to take up heavier oxygen-18.
This research wasn't able to determine if this liquid water is episodic (e.g. after a meteorite strike) or continuously present. However their findings suggested that the exchange with the liquid water happened primarily at temperatures near freezing, which may rule out some hypotheses, particularly hydrothermal vent systems, as the primary source for the water.
Methane plume observations by Curiosity and from Earth[edit source | hide]
Methane was detected in the Mars atmosphere for the first time in 2004. This stimulated follow up measurements, and research into possible biological or geological origins for methane on Mars.
If these measurements are valid (they were confirmed by three independent teams at the time), then there must be some source continually producing methane. Methane dissociates in the atmosphere through photochemical reactions - for instance it reacts with hydroxyl ions forming water and CO2 in the presence of sunlight. It can only survive for a few hundred years in the Mars atmosphere.
- 'Life in the form of methanogens (methane producing bacteria). These are autotrophs which require little more than hydrogen and carbon dioxide to metabolize. For the hydrogen source they could use a geothermal source of hydrogen, possibly due to volcanic or hydrothermal activity, or they could use the reaction of basalt and water. Methanogens have been found to be able to grow in Mars soil simulant in these conditions of water, CO2 and hydrogen., and to be able to withstand the Martian freeze / thaw cycles.
- Subsurface rocks such as olivine chemically reacting with water in presence of geothermal heat in the process known as serpentization.
- Ancient underground reservoirs, or methane trapped in ice as clathrates (with the methane originally created by either of the other two methods)
The original remote observations from Earth needed confirmation by close up inspection on Mars. When Curiosity first landed, no methane was detected to the limits of its sensitivity (implying none is present at levels of the order of parts per billion).
However around eight months later, in November 2013, Curiosity detected Methane spikes up to 9 ppb. These spikes were observed in only one measurement (the measurements were taken roughly every month) and then dropped down to 0.7 ppb again. This happened again in early 2014.
This suggests a localized source to the researchers, since there is no mechanism known that could boost the global atmospheric levels of methane so quickly for such a short time. The leading hypothesis therefore is that a plume of methane gas escaped from some location not far from Curiosity and drifted over the rover, where it detected it.
However the nature of that source is currently unknown. It could as easily be due to inorganic sources as due to life.
The ExoMars Trace Gas Orbiter may help to answer this question, as it will be able to detect trace gases such as methane in the Mars atmosphere using techniques that are about a thousand times more sensitive than any previous measurements. It is due for launch in 2016 (it is part of the same mission that will land the first ExoMars static lander technology demo prior to the main 2018 rover mission).
Once it does these measurements, then the hope is that the results would have the resolution necessary to pinpoint the geographical locations of the sources on the ground. This could then be used to target rovers for later surface missions.
One way to distinguish between biogenic and abiogenic sources of methane might be to measure the carbon-12 to carbon-14 ratio. Methanogens produce a gas which is much richer in the lighter carbon-12 than the products of serpentization.
Dry Gullies[edit source | hide]
The dry gullies on Mars were first thought by many scientists to be formed by activity of water. Nowadays, it is thought that recent gullies are formed by dry ice processes, but that many of the older dry ice gullies result from the action of water.
The hypothesis that many older gullies (but still geologically recent) were formed by action of water got strong support in January 2015. This research, while continuing to support the conclusion that the new features are formed by CO2 processes at present, suggests that the older gullies may well have been formed by floods of melt water associated with glacial melting of glaciers that form when the Mars axis tilts beyond 30 degrees. This could have happened within the last two million years (between 400,000 and two million years ago).
Then in results first released in August 2016, scientists reported that they found no evidence of polysillicates (clays) in the gullies except in case where the gullies cut through clay deposits. This strongly suggests that they were not formed from water. The Mars Opportunity rover is going to study a Martian gully close up starting in 2017, which may help resolve the question of how it formed. Meanwhile, the original idea that these gullies could have formed and maybe still be forming as a result of outflows of liquid water has come to seem increasingly unlikely.
Warm Seasonal flows (Recurrent Slope Lineae)[edit source | hide]
Many dark streaks form seasonally on Mars. Most of these are thought to be due to dry ice and wind effects. This image shows an example, probably the result of avalanche slides and not thought to have anything to do with water:
- They form on sun facing slopes in the summer when the local temperatures rise above 0C so far too warm for dry ice.
- They are not correlated at all with the winds and dust storms.
- They are also remarkably narrow and consistent in width through the length of the streak, when compared to a typical avalanche scar.
- They develop seasonally over many weeks, gradually extending down the slopes through summer - and then fade away in autumn
The leading hypotheses for these is that they are correlated in some way with the seasonal presence of liquid water - probably salty brines.
The dark streaks resemble damp patches, but spectral measurements from orbit don't detect water. One suggestion is that the water re-arranges the sand grains so causing a darkening, for instance by removing fine dust from the surface. The images were all taken in the afternoons, so it is also possible that the water flows in the early morning and that this water has evaporated when the Mars Reconnaissance Orbiter is able to take the images and do spectroscopic imaging. The streaks are also much narrower than the resolution of the spectroscopic imaging from orbit, so water could be missed for that reason also.
Slopes with the streaks are enriched in the more oxidized ferrous and ferric oxides compared with other similar slopes without the streaks, which could be the result of water. The strength of the spectral signatures of the ferrous and ferric oxides also varies according to the season like the streaks themselves. The leading hypothesis for these streaks is that they are caused by water, kept liquid by salts which reduce the freezing point of the water.
Most of them occur at higher latitudes, but in 2013 a few were also discovered in the Valles Marineres area, surprisingly close to the equator. This research turned up 12 new sites within 25 degrees of the equator, each with hundreds, or thousands of streaks.
Since the temperatures are relatively warm throughout the year at these locations, then without a mechanism for replenishment, any subsurface ice would probably have sublimated long ago. McEwen, from the team who discovered the streaks at this new location, suggested that this may be evidence for water emerging from groundwater deep below the crust. He suggests this may have implications for searches for Martian life.
Quoting from Nature:
"The temperatures there are relatively warm throughout the year, says McEwen, and without a mechanism for replenishment, any subsurface ice would probably already have sublimated."
"He says that this suggests that water may come from groundwater deep in the crust, which could have implications for Martian life: "The subsurface is probably the best place to find present-day life if it exists at all because it is protected from the radiation and temperature extremes," he says. "Maybe some of that water occasionally leaks out onto the surface, where we could see evidence for that subsurface life."
Upper map shows elevation, lower map shows albedo, and the black squares are confirmed sites of recurrent slope lineae.
"We observe the lineae to be most active in seasons when the slopes often face the sun. Expected peak temperatures suggest that activity may not depend solely on temperature. Although the origin of the recurring slope lineae remains an open question, our observations are consistent with intermittent flow of briny water. Such an origin suggests surprisingly abundant liquid water in some near-surface equatorial regions of Mars".
They were first reported in the paper by McEwan in Science, August 5, 2011. They were already suspected as involving flowing brines back then, as all the other models available involved liquid water in some form. Finally proven pretty much conclusively to involve liquid water in some form, possibly habitable if temperatures and salinity are right - after detection of hydrated salts that change their hydration state rapidly, reported in a paper published on 28 September 2015 along with a press conference . The brines were not detected directly, because the resolution of the spectrometer isn't high enough for this, and also the brines probably flow in the morning. MRO is in a slowly precessing sun-synchronous orbit inclined at 93 degrees (orbital period 1 hr 52 minutes). Each time it crosses the Mars equator on the sunny side, South to North, the time is 3:00 pm, in the local solar time on the surface, all year round. This is the worst time of day to spot brines from orbit.
Although these features are now confirmed to involve liquid water in some form, the water could be either too cold or too salty for life. At present they are treated as potentially habitable, as "Uncertain Regions, to be treated as Special Regions".
The "Special Regions" assessment says of them:
- "Although no single model currently proposed for the origin of RSL adequately explains all observations, they are currently best interpreted as being due to the seepage of water at > 250 K, with [water activity] unknown and perhaps variable. As such they meet the criteria for Uncertain Regions, to be treated as Special Regions. There are other features on Mars with characteristics similar to RSL, but their relationship to possible liquid water is much less likely"The "Special Regions" assessment says of them:
Sun warmed dust grains embedded in ice[edit source | hide]
Möhlmann originally suggested this process in 2011 as a possible way for liquid water to form on Mars, based on a mechanism that produces liquid water in similar conditions in Antarctica. As the sunlight hits the ice, it would preferentially warm up any heat absorbing dust grains trapped inside. These grains would then store heat and form water by melting some of the ice, and the water, covered by ice, would be protected from the vacuum conditions of the atmosphere.
This process could melt the ice for a few hours per day in the warmest days of summer, and melt a few mms of ice around each grain. For instance, Losiak, et al., modeled dust grains of basalt (2-200 µm in diameter) if exposed to full sunlight on the surface of the ice on the warmest days in summer, on the Northern polar ice cap, and say this about their model, in 2014: "For example, for solar constant 350 W/m2, emissivity 0.80, grain size 2 um, and thermal conductivity 0.4 W/mK melting lasts for ~300 minutes [5 hours] and result in melting of 6 mm of ice." They developed this model as a hypothesis to explain presence of extensive deposits of gypsum in the Northern polar ice cap and the dune fields around it, and concluded that, since the atmospheric pressure there is just above the triple point, this mms thin layer of liquid water could persist for a significant period of time there around grains of basalt in the middle of the day in summer.
Flow like features[edit source | hide]
These intriguing high latitude features are associated with the Martian Geysers. The geysers themselves (if that is what they are) are thought to be results of dry ice turning to gas, and the dark spots and flow like features are thought to be debris from the geysers.
However, later in the year the flow like features extend further down the slopes. The details differ for the two hemispheres. In the Southern hemisphere, all current models for this part of the process involve liquid water. In the northern hemisphere then most of the models also involve water, although the northern hemisphere flow like features form at much lower surface temperatures.
This image shows the flow like features of the southern hemisphere.
The process starts with the dark dune spots which form in early spring. Here are some examples in Richardson Crater in the Martian southern hemisphere- one of the places where the Flow Like Features (FLFs) have been observed.
These are thought to result from the Martian Geysers.
The idea is that a semi-transparent solid such as dry ice or clear ice acts like a greenhouse to warm up a layer below the surface (the "solid state greenhouse effect"). When this lower layer consists of dry ice, then it turns into gas and as the pressure builds up, eventually escapes to the surface explosively as a Martian Geyser.
The debris from these geysers form the dark spots, and the "flow like features".
Then, as local summer approaches, the flow like features start to extend down the slope. These are small features only a few tens of meters in scale, and grow at a rate of a meter or a few meters per Martian sol through the late Martian spring and summer. This is the part of the process that is thought to be due to liquid water, in nearly all the models proposed for them so far.
A different mechanism is proposed for them in the Northern and in the Southern hemispheres.
Solid state greenhouse effect model[edit source | hide]
Möhlmann uses a solid state greenhouse effect in his model, similarly to the process that forms the geysers, but with translucent ice rather than dry ice as the solid state greenhouse layer.
In his model, first the ice forms a translucent layer - then as summer approaches, the solid state greenhouse effect raises the temperature of a layer below the surface to 0 °C, so melting it. This is a process familiar on the Earth for instance in Antarctica. On Earth, in similar conditions, the surface ice remains frozen, but a layer of liquid water forms from 0.1 to 1 meters below the surface. It forms preferentially in "blue ice".
On Mars, in his model, the melting layer is 5 to 10 cm below the surface. The liquid water layer starts off millimeters thick in their model, and can develop to be centimeters thick as the season progresses. The effect of the warming is cumulative over successive sols. Once formed, the liquid layer can persist overnight. Subsurface liquid water layers like this can form with surface temperatures as low as -56 °C.
If the ice covers a heat absorbing layer at the right depth, the melted layer can form more rapidly, within a single sol, and can evolve to be tens of centimeters in thickness. In their model this starts as fresh water, insulated from the surface conditions by the overlaying ice layers - and then mixes with any salts to produce salty brines which would then flow beyond the edges to form the extending dark edges of the flow like features.
Later in the year, pressure can build up and cause formation of mini water geysers which may possibly explain the "white collars" that form around the flow like features towards the end of the season - in their model this is the result of liquid water erupting in mini water geysers and then freezing as white pure water ice.
- A way for pure water to be present on Mars, and to stay liquid under pressure, insulated from the surface conditions.
- 5 to 10 cm below the surface, trapped by the ice above it
- Depending on conditions, the liquid layer is at least centimeters in thickness, and could be tens of centimeters in thickness.
- Initially of fresh water, at around 0 °C.
If salt grains are present in the ice, then this gives conditions for brines to form, which would increase the melt volume and the duration of the melting. The brines then flow down the slope and extend the dark patch formed by the debris from the Geyser, so creating the extensions of the flow like features.
They mention a couple of caveats for their model, because the surface conditions on Mars at these locations is unknown. First it requires conditions for bare and optically transparent ice fields on Mars translucent to depths of several centimeters, and it is an open question whether this can happen, but there is nothing to rule it out either. Then, the other open question is whether their assumption of low thermal conductivity of the ice, preventing escape of the heat to the surface, is valid on Mars. The process works with blue ice on Earth - but we can't say yet what forms the ice actually takes in these Martian conditions.
This solid state greenhouse effect process favours equator facing slopes. Also, somewhat paradoxically, it favours higher latitudes, close to the poles, over lower latitudes, because it needs conditions where surface ice can form on Mars to thicknesses of tens of centimeters. (The examples at Richardson crater are at latitude -72°, longitude 179.4°, so only 18° from the south pole.).
There is no in situ data yet for these locations, of course, to test the hypothesis. Though some of the predictions for their model could be confirmed by satellite observations.
Interfacial liquid layers model[edit source | hide]
Another model for these southern hemisphere features involves ULI water (undercooled liquid water) which forms as a thin layer over surfaces and can melt at well below the usual melting point of ice. In Mohlmann's sandwich model, then the interfacial water layer forms on the surfaces of solar heated grains in the ice, which then flows together down the slope. Calculations of downward flow of water shows that several litres a day of water could be supplied to the seepage flows in this way.
The idea then is that this ULI water would be the water source for liquid brines which then flow down the surface to form the features.
Northern Hemisphere flow like features[edit source | hide]
The flow like features in the northern hemisphere polar ice cap form at average surface temperatures of around 150°K - 180°K, i.e. up to -90 °C approximately.
"They show a characteristic sequence of changes: first only wind-blown features emanate from them, while later a bright circular and elevated ring forms, and dark seepage-features start from the spots. These streaks grow with a speed between 0.3 meters per day and 7 meters per day, first only from the spots, later from all along the dune crest."
The seepage features first form at overall surface temperatures of 160°K (-110 °C), as measured with the low resolution TES data. However this has a resolution of 3 km across track and only 9 km along the track of the observations. Also, much of the area is still covered in dry ice at this point, and it is opaque in the thermal infrared band so the orbital photographs measure the temperature of the surface of the dry ice rather than the small area of the dark spots and streaks.
Then, as with the model for the Martian geysers, shortwave radiation can penetrate translucent CO2 ice layer, and heat the subsurface through the solid state greenhouse effect.
The models suggest that subsurface melt water layers, and interfacial water could form with surface temperatures as low as 180°K (-90 °C). Salts in contact with them could then form liquid brines.
An alternative mechanism for the Northern hemisphere involves dry ice and sand cascading down the slope but most of the models involve liquid brines for the seepage stages of the features.
For details see the Dark Dune Spots section of Nilton Renno's paper which also has images of the two types of feature as they progress through the season.
Life able to take up water from the 100% night time humidity of the Mars atmosphere[edit source | hide]
A series of experiments by DLR (German aerospace company) in Mars simulation chambers and on the ISS show that some Earth life (Lichens and strains of chrooccocidiopsis, a green algae) can survive Mars surface conditions and photosynthesize and metabolize, slowly, in absence of any water at all. They could make use of the humidity of the Mars atmosphere. Though the absolute humidity is low, the relative humidity at night reaches 100% because of the large day / night swings in atmospheric pressure and temperature.
Lichens relying on 100% night time humidity[edit source | hide]
The lichens studied in these experiments have protection from UV light due to special pigments only found in lichens, such as parietin and antioxidants such as b-carotene in epilithic lichens. This gives them enough protection to tolerate the light levels in conditions of partial shade in the simulation chambers and make use of the light to photosynthesize. Indeed, UV protection pigments have been suggested as potential biomarkers to search for on Mars.
An experiment on the ISS as part of Expose-E in 2008-2009 showed that one lichen, Xanthoria elegans, retained a viability of 71% for the algae (photobiont) and 84% for the fungus (mycobiont) after 18 months in the ISS, in Mars surface simulation conditions, and the surviving cells returned to 99% photosynthetic capabilities on return to Earth. This was an experiment without the day night temperature cycles of Mars and the lichens were kept in a desiccated state so it didn't test their ability to survive in niche habitats on Mars. This greatly exceeded the post flight viability of any of the other organisms tested in the experiment.
Another study in 2014 by German aerospace DLR in a Mars simulation chamber used the lichen Pleopsidium chlorophanum. This lives in the most Mars like environmental conditions on Earth, at up to 2000 meters in Antarctica. It is able to cope with high UV, low temperatures and dryness. It is mainly found in cracks, where just a small amount of scattered light reaches it. This is probably adaptive behaviour to protect it from UV light and desiccation. It remains metabolically active in temperatures down to -20 C, and can absorb small amounts of liquid water in an environment with ice and snow.
When exposed to full UV levels in a 34-day experiment in a Mars simulation chamber at DLR, the fungus component of the lichen Pleopsidium chlorophanum died, and it wasn't clear if the algae component was still photosynthesizing.
However, when partially shaded from the UV light, as for its natural habitats in Antarctica, both fungus and algae survived, and the algae remained photosynthetically active throughout. Also new growth of the lichen was observed. Photosynthetic activity continued to increase for the duration of the experiment, showing that the lichen adapted to the Mars conditions.
This is remarkable as the fungus is an aerobe, growing in an atmosphere with no appreciable amount of oxygen and 95% CO2. It seems that the algae provides it with enough oxygen to survive. The lichen was grown in Sulfatic Mars Regolith Simulant - igneous rock with composition similar to Mars meteorites, consisting of gabbro and olivine, to which quartz and anhydrous iron oxide hematite (the only thermodynamically stable iron oxide under present day Mars conditions) were added. It also contains gypsum and geothite, and was crushed to simulate the martian regolith. This was an ice free environment. They found that photosynthetic activity was strongly correlated with the beginning and the end of the simulated Martian day. Those are times when atmospheric water vapour could condense on the soil and be absorbed by it, and could probably also form cold brines with the salts in the simulated martian regolith. The pressure used for the experiment was 700 - 800 Pa, above the triple point of pure water at 600 Pa and consistent with the conditions measured by Curiosity in Gale crater.
The experimenters concluded that it is likely that some lichens and cyanobacteria can adapt to Mars conditions, taking advantage of the night time humidity, and that it is possible that life from early Mars could have adapted to these conditions and still survive today in microniches on the surface.
Black fungi and black yeast relying on 100% night time humidity[edit source | hide]
In another experiment, by Kristina Zakharova et al., two species of microcolonial fungi – Cryomyces antarcticus and Knufia perforans - and a species of black yeasts–Exophiala jeanselmei were found to adapt and recover metabolic activity during exposure to a simulated Mars environment for 7 days. They depended on the temporary saturation of the atmosphere with water vapour like the lichens. The fungi didn't show any signs of stress reactions (such as creating unusual new proteins).
There Cryomyces antarcticus is an extremophile fungi, one of several from Antarctic dry deserts. Knufia perforans is a fungi from hot arid environments, and Exophiala jeanselmei is a black yeast endolith closely related to human pathogens.
The experimenters concluded that these black fungi can survive in a Mars environment.
Deliquescing salts taking up moisture from the Mars atmosphere[edit source | hide]
Mars is rich in perchlorates - a discovery made by Phoenix, and later confirmed by Curiosity and by analysis of Martian meteorites on Earth. It now seems that perchlorates probably occur over much of the surface of Mars. This is of especial interest since perchlorates deliquesce more easily than chlorides and at a lower temperature, so they could, potentially, take up water from the atmosphere more readily.
It is not yet clear how they formed. Sulfates, chlorides and nitrates can be made in sufficient quantities by atmospheric processes, but this mechanism doesn't seem sufficient to explain the observed abundances of perchlorates on Mars.
Though there is little by way of water vapour in the Mars atmosphere, which is also a near vacuum - still it reaches 100% humidity at night due to the low nighttime temperatures. This effect creates the Martian morning frosts, which were observed by Viking in the extremely dry equatorial regions of Mars.
The discovery of perchlorates raises the possibility of thin layers of salty brines that could form a short way below the surface by taking moisture from the atmosphere when the atmosphere is cooler. It is now thought that these could occur almost anywhere on Mars if the right mixtures of salts exist on the surface, even possibly in the hyper-arid equatorial regions. In the process of deliquescence, the humidity is taken directly from the atmosphere. It does not require the presence of ice on or near the surface.
Some microbes on the Earth are able to survive in dry habitats without any ice or water, using only liquid obtained by deliquescence. For instance this happens in salt pillars in the hyper arid core of the Atacama desert. They can do this at a remarkably low relative humidity, presumably making use of deliquescence of the salts.
Perchlorates are poisonous to many lifeforms. However, perchlorates are less hazardous at the low temperatures on Mars, and some Haloarchaea are able to tolerate them in these conditions, and some of them can use them as a source of energy as well.
These layers are predicted to lie a few cms below the surface, and are likely to be thin films or droplets or patches of liquid brine. So, they probably won't be detected from orbit, at least not directly. Confirmation may have to wait until we can send landers to suitable locations with the capabilities to detect these layers. Some of the layers may form in equatorial regions, and analysis of results from Curiosity in early 2015 has returned indirect evidence for presence of subsurface deliquescing brines in Gale Crater.
Whether any of these layers are habitable for life will depend on the temperatures and the water activity (how salty the brines are), which in turn depends on conditions and the composition of salts, whether they are mixed with soil, atmospheric conditions, and even the detailed structure of the microhabitats.
Eutectic and eutonic mixtures, e.g. of chlorides and perchlorates deliquesce at a lower relative humidity, and remain liquid at a lower temperature than either separately[edit source | hide]
The possibility of liquid brines forming on Mars is improved hugely by the process of eutectic mixtures. The name comes from the Greek "ευ" (eu = easy) and "Τήξις" (tecsis = melting). If you have a mixture of two salts, for example, a mixture of chloride with perchlorate, then the mixture stays liquid at a lower temperature than each of the salts separately. The melting temperature is the "eutectic point". This phenomenon is related to the way that Antifreeze works, and the reason why salt keeps roads free from ice. See also Freezing-point depression.
Its the same with humidity, in which case it is called a eutonic mixture, or a eutonic solution (when it has taken up enough water vapour to become liquid), and the relative humidity at which this happens is the eutonic point. A mix of salts is able to take up water from drier air (lower relative humidity) than either of the salts separately, which again hugely improves the possibility of liquid brines forming by deliquescence. It doesn't matter much what the actual percentages of the two salts are, so long as there is some of both in the mixture.
Technical details of how it works[edit source | hide]
The Deliquescing Relative Humidity for a mixture of salts is the humidity needed for the entire mixture to become liquid. This varies depending on the proportion of each salt in the mixture.
The relative proportions of two salts needed to remain liquid with the lowest level of humidity is known as the eutonic point.
Any mixture of two salts, even if the proportions are well away from the eutonic point, can still take up some water vapour at this lowest level of humidity. It will continue to do this until one of the salts is entirely used up to create this optimal mixture. If there is an excess of the other salt, it remains out of solution in the solid phase.
This diagram shows how it works - for a fictitious mixture A and B.
Here DRH = Deliquescing Relative Humidity, ERH = Eutonic Relative Humidity.
E(A+B) is the optimal or Eutonic mixture. And L here refers to the liquid phase. So, to the left we have a mixture of A with E(A+B) and, once it reaches the eutonic point, only part of it is liquid, and some of the salt A will remain in its solid phase. To the right, similarly, some of the salt B remains in its solid phase above the eutonic point.
So as the humidity is increased, for a given A / B mixture, first the lower horizontal line is reached, at which point some of the mixture of salts becomes liquid. This is known as the "eutonic relative humidity" - the point at which any mixture will start to take up some water vapour.
As humidity is raised further, more and more of the mixture becomes liquid. Eventually the upper, curved line is reached - and at that point, the entire mixture will be in its liquid phase.
Similarly if the axis is temperature - then as the temperature is raised, first part of the mixture will go liquid, at a temperature corresponding to the optimal mixture of the salts, and then when the upper curved line is reached, the entire mixture will be liquid.
Effect of this[edit source | hide]
Because of this eutonic mixture effect, if you add a tiny amount of perchlorates to the less deliquescent chlorides, this is enough to reduce the minimum relative humidity needed to deliquesce to the eutonic relative humidity for the mixture. This is not only lower than the deliquescence relative humidity of the chlorides, it is also lower than the deliquescence relative humidity for the perchlorates as well.
You can also get similar eutonic mixtures of three or more different types of salts, which typically have even lower ERH than any of the mixtures of two salts. Salts on Mars could have a mixture of perchlorates, chlorates, sulfates, and chlorides and perhaps nitrates also if present, along with cations of sodium, potassium, calcium, and magnesium. So there are many possibilities to consider here.
After salt mixtures take up water, they retain it after supercooling, and reduced humidity[edit source | hide]
In addition to this, once the salt mixtures take up water, they lose it less readily, so they can stay liquid even when the humidity is then reduced again below the eutonic point (delayed efflorescence). Similarly for eutectic freezing, they can be supercooled below the temperature where they would normally freeze, and may remain liquid for some time below the eutonic point.
You get a eutectic also for freezing of a single salt, with molar concentrations. If you have a mixture of salt and water then different mixtures will freeze at different temperatures. The eutectic is the optimal mix of water and salt with the lowest freezing temperature. As you freeze a mixture, then no matter what the original concentration, some of it will remain liquid down to the freezing point of the eutectic mixture.
However, as you freeze further below that temperature, you may find that the salt continues to remain liquid. The reason for this is that for a salt to come out of solution through nucleation, it has to form a new interface between the crystal surface and the liquid, which requires energy. Once the nucleation starts, then crystallization is rapid, but the nucleation can be delayed often for many hours.
For instance, MgSO4 has a eutectic of -3.6 °C but through supercooling can remain liquid for an extra -15.5 °C below that. Here is a table of some salts likely to be found on Mars, showing the eutectic temperature for each one (with the molar concentration for the optimal eutectic concentration in brackets) and the amount of supercooling below that temperature that they found with experiments (adapted from table 2 of - omitted some of the columns).
|Salt system||Eutectic (°C)||Amount of supercooling below eutectic (°C)|
|MgSO4||-3.6 °C (1.72 m)||15.5|
|MgCl2||-33 °C (2.84 m)||13.8|
|NaCl||-21.3 °C (5.17 m)||6.3|
|NaClO4||-34.3 °C (9.2 m)||11.5|
As the salt / liquid solution cools in Mars simulation conditions, then the results can be complicated, because for instance MgSO4 releases heat in an exothermic reaction when it crystallizes. This keeps it liquid for longer than you'd expect. In their experiments, it remained liquid for twelve hours as it gradually cooled below the eutectic temperature before eventually it froze at 15.5 degrees below the eutectic temperature. In simulated Mars conditions you also have to take account of the effect of soil mixed in with the salts. Surprisingly, using Mars analogue soil, this does not reduce the supercooling and can in some cases permit more supercooling.
With some of the salt solutions, depending on chemical composition, then the supercooling produces a glassy state instead of crystallization, and this could help to protect supercooled microbes from damage.
Effects of micropores in salt pillars[edit source | hide]
In experimental studies of salt pillars in the Atacama desert, microbes are able to access liquid at extremely low relative humidities due to micropores in the salt structures. They do this through spontaneous capillary condensation, at relative humidities far lower than the deliquescence point of NaCl of 75%.
Micro-environmental data measured simultaneously outside and inside halite pinnacles in the Yungay region (table 2 from )
|Variable||Halite exterior||Halite interior|
|Mean annual RH, %||34.75||54.74|
|Maximum annual RH, %||74.20||86.10|
|Minimum annual RH, %||2.90||2.20|
The researchers, Wierzchos et al., did detailed studies with scanning electron microscopes. At 75% relative humidity then brine was abundant inside the salt pillars. As the humidity was reduced, even at 30% RH, the cyanobacteria aggregates shrunk due to water loss, but still there were small pockets of brine in the salt pillars.
"Endolithic communities inside halite pinnacles in the Atacama Desert take advantage of the moist conditions that are created by the halite substrate in the absence of rain, fog or dew. The tendency of the halite to condense and retain liquid water is enhanced by the presence of a nano-porous phase with a smooth surface skin, which covers large crystals and fills the larger pore spaces inside the pinnacles... Endolithic microbial communities were observed as intimately associated with this hypothetical nano-porous phase. While halite endoliths must still be adapted to stress conditions inside the pinnacles (i.e. low water activity due to high salinity), these observations show that hygroscopic salts such as halite become oasis for life in extremely dry environments, when all other survival strategies fail.
Our findings have implications for the habitability of extremely dry environments, as they suggest that salts with properties similar to halite could be the preferred habitat for life close to the dry limit on Earth and elsewhere. It is particularly tempting to speculate that the chloride-bearing evaporites recently identified on Mars may have been the last, and therefore most recently inhabited, substrate as this planet transitioned from relatively wet to extremely dry conditions"
Microbes also inhabit Gypsum deposits (CaSO4.2H2O), however Gypsum doesn't deliquesce. Researchers found that the regions of the desert that had microbial colonies within the gypsum correlated with regions with over 60% relative humidity for a significant part of the year. They also found that the microbes imbibed water whenever the humidity increased above 60% and gradually became desiccated when it was below that figure.
Implications of these effects[edit source | hide]
The combination of all these effects means that mixtures of salts, including perchlorates in the mixture, can be liquid at lower temperatures than any of the salts separately, and also take up water from the atmosphere at lower relative humidity, and once liquid, can remain liquid for longer than you would predict if you didn't take account of these effects. And if there are micropores in the salt deposits, any life within them could also take advantage of an internal relative humidity higher than the external humidity of the atmosphere.
On Mars the relative humidity of the atmosphere goes through extremes. It reaches 100% humidity every night in the extreme cold, even in equatorial regions. In the daytime the relative humidity becomes much less, approaching 0%, and any exposed salts would lose their liquid.
The surface temperatures of the top few cms also change enormously from day to night (more stable but lower temperatures are encountered deeper below the surface) and over the entire surface of Mars, temperatures are tens of degrees below freezing every night.
But because of these other effects these liquid layers, may resist efflorescence and remain liquid longer than you'd expect as the air dries out in the daytime, and also stay liquid longer than you'd expect through supercooling as the temperatures plummet at night.
The result is that you could have layers of liquid, on Mars, quite some way below the surface 1 or 2 cms where liquid water in its pure state can form.
So this discovery of perchlorates on Mars has major implications for presence of liquid, and so habitability.
Challenges for life in these liquid layers of deliquescing salts[edit source | hide]
Given the presence of salts, and including perchlorates, widespread over Mars, it would seem that these liquid layers must surely exist, though not yet directly confirmed by observation.
However some of these liquid layers may be too cold for life (some are liquid at temperatures as low as -90C or lower), or too salty (not enough "water activity). The main focus of research here for habitability is to find out whether there are mixtures of salts that can deliquesce on Mars at the right temperature range and with sufficient water activity for life to be able to take advantage of the liquid. The consensus so far is that though many of these would be too cold, or too salty for life, it seems possible that some of these, in optimal conditions, with the right mixture of salts and at the right depth below the surface, may also be habitable for suitable haloarchaea. The lifeforms would need to be perchlorate tolerant, and ideally, able to use it as a source of energy as well.
The conditions for these liquid layers to form may include regions where there is no ice present on the surface such as the arid equatorial regions of Mars.
Curiosity observations - indirect evidence of deliquescing salts in equatorial regions[edit source | hide]
Researchers using data from Curiosity in April 2015 have found indirect evidence that liquid brines form through deliquescence of perchlorates in equatorial regions, at various times, both at the surface, and down to depths up to 15 cms below the surface. When it leaves sandy areas, the humidity increases, suggesting that the sand takes up water vapour.
At night, the water activity is high enough for life, but it is too cold, and in the day time it is warm enough but too dry. The authors concluded that the conditions in the Curiosity region were probably beyond the habitability range for replication and metabolism of known terrestrial micro-organisms.
Advancing sand dunes bioreactor[edit source | hide]
The idea behind this proposal is that the constantly moving sand dunes of Mars may be able to create a potential environment for life. Raw materials can be replenished, and the chemical disequilibrium needed for life maintained through churning of the sand by the winds.
The sources of carbon would come from space - it is supplied at a steady rate of 5 nanograms per square meter per sol from micrometeorites. At the equator it has a mean lifetime of 300 years - but lasts longer if buried.
On the leeward side of transgressing dunes, then the sand can be buried at the rate of centimeters per year. Since the UV light only penetrates the top centimeter of the soil, then the interplanetary carbon would be buried, beyond reach of UV, within a year.
Additionally, if there was photosynthetic life or similar in the sand dunes, this could fix CO2 from the atmosphere as an additional source (there is of course no evidence for this yet).
As for water, then their idea is that the frost that forms in the morning in the equatorial regions would also occur below the surface (is no reason for it to be confined to the surface). Then, in presence of salts, the day / night temperature cycles could force this water to migrate downwards and form potentially habitable layers of brine a few centimeters below the surface.
They suggest for instance, a eutectic mixture of Mg(ClO4)2 and Ca(ClO4)2 brines which have eutectics of -71 °C and -77 °C. This is well below the lowest known temperatures for growth for terrestrial microbes, of -20 °C, but growth at lower temperatures may be possible on Mars so long as liquid is present.
Ferrous iron cold be the electron donor. And ferric iron or perchlorate could be the oxidant - electron acceptor.
The main nutrients (N, P, S) and trace nutrients (Mg, Ca, K, Fe, etc.) are all readily available with exception of N. They suggest that the dunes could have reduced nitrogen produced from the atmospheric N2 catalyzed by iron oxides in presence of UV radiation.
This is of special interest as a potential habitat that is accessible by MSL and other equatorial region rovers, as it doesn't require presence of surface ice.
In summary, their conclusion is that if MSL detects organic carbon, and reduced nitrogen compounds (which it has now done) then these sand dunes could be potential microbial habitats on present day Mars:
"Advancing martian dunes mix oxidants, reductants, water, nutrients, and possibly organic carbon in what could be considered bioreactors. Thus, martian dunes function as small scale analogues of the global geological cycles that are important in maintaining Earth's habitability. On Mars, carbon can be cycled from the surface of the dune to its subsurface where it may come in contact with moisture and oxidants. Compounds oxidized at the surface of dunes by UV radiation and oxygen are buried on the lee side of dunes and mixed with reductants, carbon, and ephemeral brines. In addition, reduced compounds will be exposed at the surface on the windward side of dunes where they can be oxidized and complete the cycle. ... Additional measurements by MSL such as detecting organic carbon and reduced nitrogen compounds would support the hypothesis that moving dunes are potential microbial habitats. The absence of these compounds would indicate that the today's dunes are unlikely to be habitable."
Droplets of liquid water on salt / ice interfaces[edit source | hide]
This is the result of a research team led by Nilton Renno, professor of atmospheric, oceanic and space sciences at Michigan University. He is also project scientist for Curiosity in charge of the REMS weather station on Mars, was also a scientist on the Phoenix lander team.
In the academic paper about this research he writes:
"The results of our experiments suggest that the spheroids observed on a strut of the Phoenix lander formed on water ice splashed during landing [Smith et al., 2009; Rennó et al., 2009]. They also support the hypothesis that “soft ice” found in one of the trenches dug by Phoenix was likely frozen brine that had been formed previously by perchlorates on icy soil. Finally, our results indicate that liquid water could form on the surface during the spring where snow has been deposited on saline soils [Martínez et al., 2012; Möhlmann, 2011]. 'These results have important implications for the understanding of the habitability of Mars because liquid water is essential for life as we know it, and halophilic terrestrial bacteria can thrive in brines'"
Ice and salt are both common in the higher latitudes of Mars, so these millimeter scale micro-habitats on salt / ice boundaries may likewise be a common feature on Mars.
Shallow interfacial layers a few molecules thick[edit source | hide]
These interfacial layers occur on boundaries between ice and rock due to intermolecular forces that depress the freezing point of the water. The water flows and acts as a solvent. These layers may be used by microbes in arctic permafrost, which have been found to metabolize at temperatures as low as -20 °C. Life may be possible in interfacial layers as thin as three monolayers, and the model by Stephen Jepsen et al. obtained 109 cells/g at -20 °C, though the microbes would spend most of their time in survival mode. Models show that interfacial water should form in some regions of Mars, for instance in Richardson crater.
Ice covered lakes that form in polar regions after large impacts[edit source | hide]
This is a possibility that was highlighted recently with the close flyby of Mars by the comet Siding Spring in 2014 C/2013 A1 Siding Spring. Before its trajectory was known in detail, there remained a small chance that it could hit Mars. Calculations showed it could create a crater of many km in diameter and perhaps a couple of km deep. If a comet like that was to hit polar regions or higher latitudes of Mars, away from the equator, it would create a temporary lake, which life could survive in.
Models suggest that a crater 30 – 50 km in diameter formed by a comet of a few kilometers in diameter would result in an underground hydrothermal system that remains liquid for thousands of years. This happens even in cold conditions so is not limited to early Mars, so a similar impact based temporary underground hydrothermal system could be created today if there was a large enough impact like Siding Spring. The lake is kept heated by the melted rock from the initial impact in hydrothermal systems fed by underground aquifers.
Temporary lakes resulting from volcanic activity[edit source | hide]
There is evidence that volcanism formed lakes 210 million years ago on one of the flanks of Arsia Mons, relatively recent in geological terms. This may have consisted of two lakes of around 40 cubic kilometers of water, and a third one of 20 cubic kilometers of water, which probably remained liquid for hundreds, or even of the order of thousands of years.
Possibility of geological hot spots in present day Mars[edit source | hide]
There is clear evidence that Mars is not yet geologically inactive
- Small scale volcanic features associated with some of the volcanoes on Mars which must have formed in the very recent geological past
- The isotopic evidence from Phoenix of release of CO2 in the recent geological past.
It seems likely that there are magma plumes at least deep underground, associated with the occasional surface volcanism on the geological timescale of millions of years. And given that there has been activity on Olympus Mons as recently as four million years ago, it seems unlikely that all activity has stopped permanently.
But so far no currently active volcanism has been observed, nor have any present day warm areas have ever been found on the surface, in extensive searches. The Mars Global Surveyor scanned most of the surface in infrared with its TES instrument. The Mars Odyssey's THEMIS, also imaged the surface in wavelengths that measure temperature.
Another way to search for volcanic activity is through searches of trace gases produced in volcanic eruptions. So far nothing has been observed from Earth but instruments are limited in their sensitivity and get only limited observing time for Mars as well. This is going to be a focus of future searches however. One of the instruments on the 2016 ExoMars Trace Gas Orbiter is NOMAD (Nadir and Occultation for Mars Discovery), which will search for trace gases indicating current volcanic activity, as well as searching directly for organics that could result from life processes, and the methane plumes.
If these hot spots exist, they could keep water liquid through geothermal heating. The water could be trapped under overlying deposits and kept at a pressure high enough to stay liquid. They could also be a source for intermittent surface or near surface water (for instance one of the hypotheses for the RSLs is that they may be occur over geological hot spots deep below the surface that indirectly supply them with water).
Another possibility is a volcanic ice tower - a column of ice that can form around volcanic vents, for instance on Mount Erebus, Ross Island, Antarctica. These would be only a few degrees higher in temperature than the surrounding landscape so easy to miss in thermal images from orbit.
Potential for cave habitats on Mars[edit source | hide]
As well as the lava tube caves, Mars may have other caves also less visible from orbit. It has most of the same processes that form caves on the Earth, and also has processes unique to Mars that may also create caves, for instance through direct sublimation of ice or dry ice into the atmosphere. Caves are of especial interest on Mars for astrobiology, because they can give protection from some of the harsh surface conditions. If the caves are isolated from the surface, or almost isolated, they may have conditions similar to similarly isolated caves on the Earth.
In the "Workshop on Mars 2001", the main possibilities for cave formation listed are:
"(1) diversion of channel courses in underground conduits; (2) fractures of surface drainage patterns; chaotic terrain and collapsed areas in general; (4) seepage face in valley walls and/or headwaters; (5) inactive hydrothermal vents and lava tubes."
They remark that caves that formed at headwaters or where liquid seeped from the rocks may be of special interest for astrobiology, and these may be places where some ice would still be present. Of course research has moved on since 2001.
In 2014, Penelope Boston (director of the NASA Astrobiology institute since 2016, microbiologist and speleologist) lists some of the main possible types of cave. She divides into the four main categories which she then divides into further subcategories.
- Solutional caves (e.g. on Earth, caves in limestone and other materials that can be dissolved, either through acid, or water)
- Melt caves (e.g. lava tubes and glacier caves)
- Fracture caves (e.g. due to faulting)
- Erosional caves (e.g. wind scoured caves, and coastal caves eroded by the sea)
- Suffosional caves - a rare type of cave on the Earth, where fine particles are moved by water, leaving the larger particles behind - so the rock does not dissolve, just the fine particles are removed.
She points out a few processes that may be unique to Mars. Amongst many other ideas she suggests:
- For the solutional caves, the abundance of sulfur on Mars may make sulfuric acid caves more common than they are on Mars. There's also the possibility of liquid CO2 (which forms under pressure, at depth, e.g. in a cliff wall) forming caves.
- For the melt caves, then the lava tubes on Mars are far larger than the ones on the Earth.
- Mars could have sublimational caves caused by dry ice and ordinary ice subliming directly into the atmosphere.
Some cave habitats on Earth, if shielded from the surface, may be almost exact duplicates of similar habitats on Mars. For instance the Snottites in the toxic sulfur cave Cueva de Villa Luz flourish on Hydrogen Sulfide gas. Some of these species are aerobes (needing only small amounts of oxygen), and others are anaerobes and could survive anywhere on Mars where similar habitats exist. Mars has been shown to be geologically active in the recent geological past through the Phoenix isotope measurements. Although there are no currently known geological hotspots or activity is currently known, there may well be subsurface thermal systems where caves similar to the Cueva de Villa Luz could occur.
Sub surface ice sheets in the equatorial regions[edit source | hide]
As the axial tilt of Mars changes, at times it tilts so far that it has equatorial ice sheets instead of polar caps.
Several lines of evidence suggest, that Mars may have remnant subsurface equatorial ice sheets today. The first evidence of this was based on radar measurements from the (MARSIS) instrument aboard the Mars Express Spacecraft in 2007. These detected subsurface deposits that had similar density and dialectric constant to a mixture with more dust and sand than the polar ice deposits, and similar in volume and extent.
Other papers have provided additional, but not yet conclusive evidence that these may indeed be deposits of ice. For instance a 2014 paper reports observations of young ring-mold craters on tropical mountain glacier deposits on the flanks of Arsia and Pavonis Mons. Ring-mold craters are distinctive features that result from impact into debris covered ice. The observations suggest presence of remnant equatorial ice, over 16 meters below the surface.
Ice in the equatorial regions would normally be lost through sublimation into the near vacuum of the Mars atmosphere, to a depth of a hundred meters or more, and this happens quite rapidly over geological timescales, over timescales of order of 100,000 years or so. So for remnant ice to survive there today, then special conditions are needed. For instance trapped ice beneath an impervious layer (capstone). Or replenished from below. This is a matter for active research with no established conclusions yet.
Hydrosphere - possible layer of liquid water several kilometers below the surface[edit source | hide]
Deep rock habitats on Earth are inhabited by life so may also be on Mars. However they need liquid water to survive, which may possibly exist below the cyrosphere.
The Mars cryosphere is the layer of permanently frozen permafrost. In higher latitudes it starts a few cms below the surface, and may continue down for several kilometers. In equatorial regions the surface of Mars may be completely dry down to a kilometer or more, so the cryosphere starts at the base of that dry layer.
If the Mars hydrosphere exists, it lies below the cryosphere, and is a layer where the ice is kept liquid by geothermal heating, and prevented from evaporating by the overlying layers of ice.
We don't have any evidence yet of a hydrosphere, but do have evidence of a deep subsurface cryosphere. This evidence is in the form of hydrogen / deuterium isotope ratios in Martian meteorites, which give indirect evidence that Mars must have a subsurface reservoir of water, most likely in the form of ice.
If the hydrosphere exists, estimates in a paper from 2013 put its depth at around 5 kilometers below the surface. Whether this layer exists or not depends on the presence or otherwise of perchlorates, and clathrates, and it also depends on the total inventory of water on Mars, so there are many unknowns in the models. They used an estimate of the total inventory of less than 500m GEL (Global Equivalent Layer), and doubled the required thickness of the cryosphere, which leaves less water available for the hydrosphere than in previous models. There may still be groundwater in places where it is perchlorate rich, and isolated pockets.
But if the global inventory of water is larger than the amount they assumed for their study, there may be ground water under much of the surface of Mars.
If this hydrosphere exists, then it may be more habitable than similar depth zones on Earth because of the lower gravity, leading to larger pore size. Possible metabolisms at this depth could use hydrogen, carbon dioxide, and possibly abiotic hydrocarbons. The carbon for biomass could come from magmatic carbon in basalts which has been detected in Martian meteorites. It could also support methanogens feeding off methane released from serpentinization, and the alteration of basalt could also be a basis for iron respiration.
Similar habitats on Earth are inhabited by microbes and even multi-cellular life. So this is a potential habitat of astrobiological interest on Mars. As well as that, if the habitat exists it is a possible reservoir that could replenish surface areas of Mars with life and permit lifeforms to transfer from one part of Mars to another subsurface - a process that is known to happen beneath arctic permafrost layers.
It is not feasible to drill down to sample it in the near future. However, liquid may be released to the surface as a result of impact fracturing and other events so making it possible to sample it via surface measurements.
One prime place to visit to search for evidence of the deep hydrosphere is McLaughlin Crater. The observations suggest it contained an ancient lake, with alteration minerals rich in Fe and Mg, and the detection of carbonates there suggests that the fluids were alkaline, and are consistent with the expected composition of fluids that emerged from the deep subsurface hydrosphere. The Nature article concludes "Lacustrine clay minerals and carbonates in McLaughlin Crater might be the best evidence for groundwater upwelling activity on Mars, and therefore should be considered a high-priority target for future exploration"
Habitability factors for life on Mars[edit source | hide]
This section is organized around the listing of the main factors limiting surface and near surface life on Mars, according to Schuerger
These are thought to be (not in order of importance):
- Extreme desiccation and scarcity of water - all life on Earth requires liquid water - or else high humidity in the air. So the main focus for the search for present day life on Mars so far starts with this assumption. There may be other possibilities for exotic life that don't use water, for instance a recent suggestion that life may be able to evolve in supercritical liquid CO2 under high pressure - a potential habitat present on both Venus and Mars. So probably we shouldn't rule out the possibility of other habitats totally.
- UV light for any life on the surface exposed to full sunlight. Because of the thin atmosphere, this is hardly filtered at all, and is a major challenge for any life exposed to the light. It is easily blocked by about 0.3 mm of surface soil, sheltered by a millimeter of dust or by other organisms, or in the shadow of a rock. Mars conditions are likely to favour lifeforms that can tolerate high levels of UV radiation, at least, if they are exposed to direct unfiltered sunlight at any point in their life cycle. This could for instance involve use of protective pigments such as melanin, parietin and usnic acid which help protect some lichens from the damaging effects of UV radiation in polar and high alpine regions.
- Low pressures (hypobaria) at 1–14 mbar
- Anoxic CO2-enriched atmosphere. All the habitats suggested so far require anaerobes - lifeforms that don't require oxygen.
- Low temperatures. There may be some warmer locations, for instance using geothermal heating. Also, surface temperatures in equatorial regions at times reach 30C on Mars, but at these temperatures the relative humidity of the atmosphere is low and any liquid exposed to such temperatures would soon evaporate. Most of the proposed habitats require Psychrophiles - microbes that are comfortable in low temperature conditions. This is a limiting factor especially for some of brines, which may be liquid at temperatures too low for life on Earth.
Other authors also cite:
- Lack of nitrogen. All life on Earth requires nitrogen. Also there are theoretical reasons for expecting alien organic life to use nitrogen, as the weaker nitrogen based amide bonds are essential for the processes by which DNA is replicated. Mars, compared with Earth, has little nitrogen, either in the air or in the soil. Levels of nitrogen in the air are low, possibly too low for nitrogen fixation to be possible. But they can form in Martian conditions by non biological processes - either brought to Mars by meteorites (some carbonaceous chondrites are rich in nitrogen), or comets, or formed by lightning, or through atmospheric processes, or there may be ancient nitrate deposits from early Mars, amongst various possible sources.
Life on Mars may be limited to locations with local abundance of nitrates. Or, it may also be able to take advantage of fixation of nitrogen in monolayers of water, a process that can happen in present-day Mars conditions, and may be able to produce enough nitrates to supply a subsurface biosphere.
Schuerger also mentions:
- Cosmic radiation - this is not limiting of surface life in the short term (similar to the levels inside the ISS) but prevents it from reviving if kept dormant for periods of order of hundreds of thousands of years. Martian surface or near surface life is likely to be strongly resistant to cosmic radiation, with repair mechanisms to repair the damage.
Curiosity measured ionizing radiation levels of 76 mGy a year. This level of ionizing radiation is sterilizing for dormant life on the surface of Mars. However, it varies considerably in habitability depending on its orbital eccentricity and the tilt of its axis. If the surface life has been reanimated as recently as 450,000 years ago, which is possible, then our rovers on Mars could find dormant but still viable life at a depth of only one meter below the surface, according to an estimate in the paper that published the Curiosity ionizing radiation measurements. Modern researchers do not consider that ionizing radiation is a limiting factor in habitability assessments for present-day non-dormant surface life. The level of 76 mGy a year measured by Curiosity is similar to levels inside the ISS. In the 2014 Findings of the Second MEPAG Special Regions Science Analysis Group, their conclusion was:
"From MSL RAD measurements, ionizing radiation from GCRs at Mars is so low as to be negligible. Intermittent SPEs can increase the atmospheric ionization down to ground level and increase the total dose, but these events are sporadic and last at most a few (2–5) days. These facts are not used to distinguish Special Regions on Mars."
Here a SPE is a Solar Proton Event (solar storm) and a GCR is a Galactic Cosmic Ray. A "Special Region" is defined as a region on the Mars surface where Earth life could potentially survive.
Other conditions that apply locally, rather than globally include:
- High salinity is a factor for any life within the salty brines - many of the proposed surface habitats are salty and could only be inhabited by Halophiles - microbes that are comfortable with high levels of salinity, such as Halobacteria.
- The pH (acidity) and Eh (oxidation potential) of any available liquid water
- presence of heavy metals
- acidic conditions in some soils
- oxidizing soils created by soil chemical reactions rather than UV (e.g. by anoxic hydration of pyrite)
- UV-induced volatile oxidants (e.g. O2, O, H2O2, NOx, O3).
- Perchlorates. At high temperatures perchlorates are extremely oxidising and dangerous to life. But at the low temperatures of the Mars surface, then they are not so damaging and could actually be a benefit for microbes as an energy source. For a modern view on them, Cassie Conley, planetary protection officer for NASA is quoted in The New York Times as saying:
"The salts known as perchlorates that lower the freezing temperature of water at the R.S.L.s, keeping it liquid, can be consumed by some Earth microbes. “The environment on Mars potentially is basically one giant dinner plate for Earth organisms,” Dr. Conley said."
Lowest temperature for life on Mars[edit source | hide]
Based on the capabilities of Earth microbes, the usually cited lowest temperature for life is -20 °C. However, there is indirect evidence of continuing bacterial activity in glaciers down to -40 °C, at a very low metabolic rate of ten turnovers of cellular carbon per billion years.
There can be some activity at even lower temperatures. In an experiment to test incorporation of the amino acid Leucine, Karen Junge et all used two controls at -80 °C and -196 °C, well below the eutectic freezing point of salt, and to their surprise, they found that the Colwellia psychrerythraea strain 34H was able to continue to incorporate low levels of Leucine right down to -196 °C. They hypothesize that the Leucine enters the cell boundaries at higher temperatures in the first few seconds of the experiment, then gets incorporated into the cell at lower temperatures (it doesn't get incorporated right away as they proved through zero time controls).
Price et al. did a review of the literature to date, in 2004, and came to the conclusion that there is no evidence of a fixed lowest temperature limit to metabolism, in the presence of impurities and thin films of water to supply liquid to microbes.
"Our results disprove the view that the lowest temperature at which life is possible is ≈-17°C in an aqueous environment, as well as the remark that “the lowest temperature at which terrestrial and presumably martian life can function is probably near -20°C. Our data show no evidence of a threshold or cutoff in metabolic rate at temperatures down to -40°C. A cell resists freezing, due to the “structured” water in its cytoplasm. Ionic impurities prevent freezing of veins in ice and thin films in permafrost and permit transport of nutrient to and products from microbes. The absence of a threshold temperature for metabolism should encourage those interested in searches for life on cold extraterrestrial bodies such as Mars and Europa."
Lowest water activity level for life on Mars[edit source | hide]
The amount of water available for microbes to use in a salty or sugary solution is known as its water activity level which is normally expressed as the ratio of the partial vapour pressure of the water in the solution to the vapour pressure of pure water at the same temperature.
Honey has a low water activity level of 0.6. That's why honey doesn't spoil - you don't need to keep honey in a fridge, because its water activity level is so low that though microbes would find plenty to eat, and though there is plenty of water there in the honey, the water is not available to the microbes because of the low water activity level.
The fungus Xeromyces bisporus can tolerate a water activity level of 0.605 in sugar - first discovered in a 1968 study of spoilage in prunes. It can divide at these low water activity levels, so can germinate, but needs higher levels of water to create fungal spores through asexual sporulation and even more for sexual sporulation.
Until recently, it was thought that that was an isolated case, as no other microbe was known able to tolerate such levels. The usually accepted lower limit was 0.755 for halophiles. However over the last few years there have been many reports of microbes at lower activity levels than that, comparable to Xeromyces bisporus, in salt solutions. Some papers have suggested the possibility of cellular reproduction at even lower levels.
In a recent 2014 survey paper of the literature on the subject "Multiplication of microbes below 0.690 water activity: implications for terrestrial and extraterrestrial life", the authors came to the conclusion that the best consensus at present is that the lowest level of water activity needed for cell division is about 0.605, and that some halophiles are able to tolerate such low levels. They remark on the difference between the situation for water activity and the situation for temperatures, where there is much better evidence of microbes able to tolerate temperatures below the usually cited -20 °C.
Challenge of ionizing radiation[edit source | hide]
Radioresistant microbes are able to repair damage due to the equivalent of several hundred thousand years of Mars surface cosmic radiation within a few hours of revival from dormancy (they don't need to reproduce to do this, they repair their own DNA). For details: ionizing radiation resistance (radiodurans). This mechanism seems to be a byproduct of desiccation resistance, since the microbes have no need to tolerate high levels of cosmic radiation - shielded by the Earth's magnetosphere and atmosphere. Martian microbes are likely to have similar mechanisms, this time evolved in the presence of ionizing radiation.
At times the Mars atmosphere is thicker than it is now depending on variations in its orbital eccentricity and axial tilt. At other times it has extensive ice sheets which then melt. Research in January 2015 by Dickson et al. suggests that the Mars axial tilt has varied beyond the 30 degrees to the point where it has thin glacier like ice sheets at the mid latitudes within the 400,000 to 2 million years, and that this may have carved some of the older gully systems through melt water.
That's still challenging for life with a maximum of around 500,000 years dormancy on the surface. However the cosmic radiation only penetrates a few meters into the ground, with most of the effects shielded in the top 1.5 meters (400 grams per cm2 of material, at 2.6 grams per cm3 typical regolith density) and significant shielding at a depth of half a meter. Below that depth, there could be dormant microbes that have survived for longer periods. Depending on the depth below the surface they could remain dormant for millions of years. Some microbes on Earth have lasted for many millions of years in ice and salt, and have been revived. So some of these on Mars also may still be viable today. Such microbes could also survive in caves on Mars in dormancy, or in subsurface locations kept habitable by geothermal hot spots, until times when Mars is more habitable than it is today.
If there is present day life on the Mars surface, these effects of ionizing radiation suggest that it has to
- Be replenished from the subsurface
- Or be able to reproduce in surface or near surface conditions with dormancy periods never longer than 500,000 years or so.
In the 2014 MEPAG classification of special regions, ionizing radiation was not considered limiting for classifying the "Special regions" where present day surface life might survive.
Views on the possibility of present day life on or near the surface[edit source | hide]
It is a challenge for life to survive on the surface, or the near subsurface, because of the hyper arid conditions, combined with low temperatures. Often when the temperature is high enough for cellular division, the humidity is too low and vice versa. Also in surface conditions, it is not possible for microbes to remain in dormancy through the changes in axial tilt when the Mars atmosphere becomes thicker and more habitable (as it does from time to time).
Authors in recent publications present a variety of views on the possibility of present-day life on the surface of Mars or in the near subsurface.
- Unlikely - these authors cite the inability of microbes to survive dormancy on the surface between periods when the atmosphere is thicker, due to ionizing radiation, the ephemeral nature of surface habitats, low temperatures, or low relative humidity, and the difficulty of colonization in surface conditions of high UV...
- Possible, recolonized from below, these point out the ability of micro-organisms to repair damage by ionizing radiation and capability to remain dormant for up to several million years in the deep subsurface, suggesting that these short lived surface habitats, such as the Recurring Slope Lineae, could be recolonized from the subsurface.
- Possible, open question if it occurs on the surface these are investigating the possibility with experiments in simulated Mars conditions, theoretical models and study of the observations from Mars, and treat it as an open question for now, whether the present day surface and near sub surface is habitable. (Crisler, J.D.; Newville, T.M.; Chen, F.; Clark, B.C.; Schneegurt, M.A. (2012). "Bacterial Growth at the High Concentrations of Magnesium Sulfate Found in Martian Soils". Astrobiology. 12 (2): 98–106. Bibcode:2012AsBio..12...98C. doi:10.1089/ast.2011.0720. ISSN 1531-1074. PMC . PMID 22248384.</ref>
and many others).
- Likely Some researchers, particularly the researchers at DLR consider that their experiments have already shown a high likelihood that the surface of Mars is habitable, for some lichens and cyanobacteria, taking advantage of the night time humidity, and even in equatorial regions such as Gale crater. See #Life able to take up water from the 100% night time humidity of the Mars atmosphere
- Strong possibility that it has already been detected on the surface A small minority of authors believe that their reanalysis of the Viking Labeled Release experiments already indicates a strong possibility of detection of the presence of life on present day Mars, see #Viking observations - did Levin's labeled release experiment find life?
There is greater agreement on deep subsurface habitats since conditions there may be similar to Earth conditions. They would be protected from UV, cosmic radiation, and the low pressure of the atmosphere, and water activity would be likely to be similar to Earth. For instance the deep hydrosphere (if it exists), or temporary lakes that form after impacts or volcanic eruptions, seem likely to be habitable, by analogy with similar habitats on Earth.
Plausible microbial metabolisms for present day Mars[edit source | hide]
One way to examine the possibility for life on Mars is to look at the Redox pathways that the life could use as a source of energy. This involves a pairing of an electron donor and an electron acceptor. For details see Electron transport chain, and Microbial metabolism.
Here is a table of some of the available donors and acceptors in Mars conditions, table from (added CO2).
|electron donors, any of:||electron acceptors, any of:|
2: available in Fe-rich silicates
3: available in numerous alteration
|H2: available in subsurface?||SO2−|
4 available in salts
|CO: available in atmosphere||O2: partial pressure too low|
|organics: meteoritic likely to be present at surface||NO−|
3: presence or abundance unknown
|organics: endogenous available in subsurface||ClO−|
4: available but not shown to support life
|-||CO2: in the atmosphere|
A candidate metabolism would use one of the electron donors in the first column paired with one of the electron acceptors on the right as a source of energy. (The final dash on left hand side is there just because the list of electron donors is shorter than the list of electron acceptors).
See also the presentations in: Redox Potentials for Martian Life
Candidate lifeforms for Mars[edit source | hide]
This is a list of some of the proposed Mars analogue lifeforms, which may be capable of living on Mars (if the postulated liquid water habitats there exist).
Top candidates for life on Mars include
- Chroococcidiopsis - UV and radioresistant can form a single species ecosystem, and only requires CO2, sunlight and trace elements to survive.
- Halobacteria - UV and radioresistant, photosynthetic (using a different mechanism), can form single species ecosystems, and highly salt tolerant. Some are tolerant of perchlorates and even use them as an energy source, examples include Haloferax mediterranei, Haloferax denitrificans, Haloferax gibbonsii, Haloarcula marismortui, and Haloarcula vallismortis
- Some species of Carnobacterium extracted from permafrost layers on Earth which are able to grow in Mars simulation chambers in conditions of low atmospheric pressure, low temperature and CO2 dominated atmosphere as for Mars.
- Geobacter metallireducens - it uses Fe(III) as the sole electron acceptor, and can use organic compounds, molecular hydrogen, or elemental sulfur as the electron donor.
- Alkalilimnicola ehrlichii MLHE-1 (Euryarchaeota) - able to use CO in Mars simulation conditions, in salty brine with low water potentials (−19 MPa), in temperature within range for the RSL, oxygen free with nitrate, and unaffected by magnesium perchlorate and low atmospheric pressure (10 mbar). Another candidate, Halorubrum str. BV (Proteobacteria) could use the CO with a water potential of −39.6 MPa
- black molds The microcolonial fungi, Cryomyces antarcticus (an extremophile fungi, one of several from Antarctic dry deserts) and Knufia perforans, adapted and recovered metabolic activity during exposure to a simulated Mars environment for 7 days using only night time humidity of the air; no chemical signs of stress.
- black yeast Exophiala jeanselmei, also adapted and recovered metabolic activity during exposure to a simulated Mars environment for 7 days using only night time humidity of the air; no chemical signs of stress.
- Methanogens such as Methanosarcina barkeri - only require CO2, hydrogen and trace elements. The hydrogen could come from geothermal sources, volcanic action or action of water on basalt.
- Lichens such as Xanthoria elegans, Pleopsidium chlorophanum, and Circinaria gyrosa - some of these are able to metabolize and photosynthesize slowly in Mars simulation chambers using just the night time humidity, and have been shown to be able to survive Mars surface conditions such as the UV in Mars simulation experiments.
- Microbial life from depths of kilometers below the surface on the Earth that rely on geochemical energy sources - relying on metabolic pathways that can't be traced back to the sun at all. Some of these are multi-cellular. Examples include the microbe Desulforudis audaxviator which metabolizes reduced sulfur as the electron acceptor, and hydrogen as the electron donor, can fix nitrogen and has every pathway needed to synthesize all the amino acids
- Multicellular life from depths of kilometers below the surface such as Halicephalobus mephisto, a nematode feeding on bacteria, 0.5 mm long and up to 3.5 km deep, lives in water at 48 °C, very low oxygen levels about a thousandth of the levels in oceans. Though it probably originates from the surface, carbon dating shows it has lived at those depths for between 3,000 and 10,000 years, and it has been suggested that this has implications for deep subsurface multi-cellular life on Mars.
Most of these candidates are single cell microbes (or microbial films). The closest Mars analogue habitats on Earth such as the hyper arid core of the Atacama desert are inhabited by microbes, with no multicellular life. So even if multicellular life evolved on Mars, it seems that most life on Mars is likely to be microbial.
Because of the low levels of oxygen of 0.13% in the atmosphere, and (as far as we know) in any of the proposed habitats, all the candidate lifeforms are anaerobes or able to tolerate extremely low levels of oxygen. This also makes multicellular animal life unlikely, though not impossible as there are a few anaerobic multi-cellular creatures. Some multicellular plant life such as lichens, however, may be well adapted to Martian conditions (the algae supply oxygen for the fungus). Also some multicellular life such as Halicephalobus mephisto can survive using very low levels of oxygen which may perhaps be present in some Mars habitats.
Expose R2 test of candidate lifeforms for Mars on exterior of ISS[edit source | hide]
Several lifeforms, including cyanobacteria Nostoc sp. Gloeocapsa Chroococcidiopsis sp., lichens Buelia frigida, Circinaria gyrosa, and fungi Cryomyces antarcticus, are currently being tested in the ongoing year and a half Expose-R2 experiments in a small Mars simulation chambers on the exterior of the ISS (Expose R2) as part of BIOMEX (Biology and Mars Experiment).
Some of these simulation chambers are kept with atmosphere and filters to simulate Mars conditions of UV, and in some of the chambers they are in Mars simulation soil to simulate the Mars surface. Others are exposed to vacuum, e.g. to test panspermia hypotheses. The Mars simulations don't simulate the variations of atmospheric pressure and relative humidity between day and night since they are fixed volume chambers, nor do they simulate the presence of ice, evaporates, or thin film brine layers.
Test samples include bacteria and biofilms, cyanobactera, archaea, green algae, lichens, fungi, bryophytes, and yeast that have been found to be especially resistant in ground experiments and previous experiments on the ISS. They also include pigments and cell wall components.
The experimenters are studying the same organisms in Mars simulation chambers on the ground. The experiment has multiple goals - to find out what species could survive transfer to another planet on a meteorite (panspermia), to find out what detectable biosignatures would remain after exposure to space and to Mars surface conditions, and to find out their ability to survive in these conditions and possible genetic changes.
EXPOSE-R2 results[edit source | hide]
- The light-protective carotenoid pigments (present in photosynthetic organisms such as plants, algae, cyanobacteria and in some bacteria and archaea) have been classified as high priority targets for biosignature models on Mars due to their stability and easy identification by Raman spectroscopy. In this experiment, the light-protective carotenoids in two organisms (cyanobacterium Nostoc sp. and the green alga cf. Sphaerocystis sp.) were still detectable at relatively high levels after being exposed for 15 months.
- Dried biofilms of three desert strains of Chroococcidiopsis showed overall higher viability and lower amounts of DNA damage when compared to multi-layer films of the planktonic counterpart, and were consistent with ground Mars simulation experiments. The strains tested were CCMEE 029 from the Negev Desert, where they live beenath the surface of rocks (endoliths) and strains CCMEE 057 and CCMEE 064 from the Sinai Desert where they are both enndoliths and hypoliths (within rocks or on the ground sheltered beneath rocks).
- Other results are expected to be published in Frontiers in Microbiology under the research topic title: "Habitability Beyond Earth", and in an upcoming special collection of Astrobiology journal.
Uninhabited habitats[edit source | hide]
Charles Cockell has analysed the possible trajectories for life on Mars using the idea of an "uninhabited habitat". On Earth these are exceedingly rare, but do occur sometimes. For instance, after a new lava flow, then the lava may initially be inhabitable but uninhabited.
It is possible to test the hypothesis that these habitats exist by finding environments on Mars with the elements needed for life, including an energy source and liquid water, with no active life.
So then there are three states for Mars:
- Uninhabitable - doesn't have the conditions for life
- Has habitats but they are all uninhabited
- Has at least some habitats with life
As Mars evolved, initially when it first formed in the early solar system, it was too hot for life, and so was uninhabitable. Then there are various trajectories it could follow after that, starting from the early Mars. In his paper "Trajectories of Martian Habitability" he identifies six main possible trajectories. T
- "Trajectory 1. Mars is and was always uninhabitable."
- "Trajectory 2. Uninhabited Mars has hosted uninhabited habitats transiently or continuously during its history."
- "Trajectory 3. Uninhabited Mars was habitable and possessed uninhabited habitats but is now uninhabitable."
- "Trajectory 4. Mars is and was inhabited."
- "Trajectory 5. Mars was inhabited, life became extinct, but uninhabited habitats remain on Mars."
- "Trajectory 6. Mars was inhabited, life became extinct, and the planet became uninhabitable."
He also suggests other more complex trajectories. For instance that it starts with uninhabited habitats and the life evolves there at a much later date, or is seeded from Earth at a later date. Or trajectories where life on Mars becomes extinct, and then reoriginates on Mars or is transferred to Mars from Earth. Or even, a logical possibility but seems unlikely, that it was for some reason uninhabitable in the early Noachian and became habitable later.
In his paper he discusses ways that this could be tested with observations. For instance, if you find that promising environments with water in present-day and past Mars lacked some fundamental requirement for all known life, or the conditions were outside the range of physical and chemical tolerances of all known organisms, then that could be evidence for trajectory 1. If you find conditions for life but no life, past or present, that's evidence for trajectory 2, and so on.
He points out that if Mars does have uninhabited habitats, these would be a useful control to investigate the role of biology in planetary scale biological processes on Earth.
Also to cover the pre-biological investigations in case that habitats are found that are habitable but with no life in them.
GOAL 3—Understand how life emerges from cosmic and planetary precursors. Perform observational, experimental, and theoretical investigations to understand the general physical and chemical principles underlying the origins of life.
Characterize the exogenous and endogenous sources of matter (organic and inorganic) for potentially habitable environments in the Solar System and in other planetary and protoplanetary systems.
Search for a second genesis of life on Mars[edit source | hide]
The search for life on Mars is of special interest for the search for a second example of life, which can help us to discover which of the many common shared features of the biochemistry of Earth organisms are essential for life, and which are accidents of evolution. Chris McKay puts it like this in his 2010 article "An origin of life on Mars.":
"The search for a second example of life is a key goal for astrobiology. All life on Earth shares common biochemistry and descends from a common ancestor. This prevents us from understanding which aspects of biochemistry and genetics are essential features of life and which are merely particular to the evolutionary history of life on this planet. To develop a more general understanding of life, we need more than one example. Hence, we hope that Mars may have been the site of an independent origin of life."
Until recently, it was assumed that any life on Mars would necessarily be a second genesis. But it is now understood that life could be transferred between planets on meteorites, so it is possible that life on Mars, if it exists, could be related to Earth life, or some of the life could be related to Earth life.
In order to decide whether the life is a second genesis or not, it is not enough to examine fossils. For one thing, microbes often don't form easily recognized convincing fossils, so the fossils may be hard to recognize, and rare in occurrence. But as well as that, fossils don't tell us what the chemical basis is for the life.
It is necessary to be able to study organics, and it preferably, viable cells. If life on Mars had same chirality, genetic code, choice of amino acids, lipids and so on, that would be evidence of a shared ancestry. If any of those differ, then it is likely to represent a second genesis.
Writing in 2010, Chris McKay says
"Possible targets include: (1) Life in the surface soil, (2) Life in subsurface liquid water, (3) Organisms, probably dead, but preserved in ancient salt or mineral deposits, and (4) Organisms, dead or alive, preserved in ancient ice."
Organics are common throughout the outer solar system, including meteorites, and comets. So when organics are found on Mars, the first thing to be decided is whether or not it is biological in origin. If it is related to Earth life, and sufficiently well preserved, this can be detected though search for DNA, RNA, ATP and other key molecules associated with life on Earth. But if it is not related to Earth life, then it may be harder to decide whether it is the result of biological processes.
One way to detect alien biology may be through the "Lego principle". This is the idea that chemicals used by life may be recognized because they use a wide range of chemicals with similar chemical structure, and chemicals very similar to each other (e.g. only differing in chirality) may have widely different concentrations. This is something that could be recognized even if the life has a different chemical basis from Earth life.
However, over time, the pattern degenerates as chemical bonds break and reform, especially in warmer conditions. So ideally we need to find life that is either alive, or has been preserved in cold conditions since it was deposited.
In his 2010 article, Chris McKay suggests targeting possibly still viable organisms preserved in ancient subsurface ice. This is also the main target for his proposed mission Icebreaker Life.
Even a null result in search for life on Mars would be of astrobiological significance. For instance it might tell us that the origins of life depend on particular conditions not present on Mars. For instance that it depends on a particular energy source, or material or on abundance of some particular nutrient (e.g. nitrogen).
Planetary protection issues[edit source | hide]
Search for present day life on Mars requires more stringent planetary protection than the search for past life. For instance, if Curiosity were to discover traces of liquid water on Mars, in some microhabitat in conditions that make it potentially habitable to Earth life, it would not be able to approach it to measure it to search for present day life as it is not sufficiently sterilized for this task. And indeed it encountered exactly this situation when they found evidence of a possible RSL on Mount Sharp. Curiosity will probably not be permitted to approach it closer than a distance of a few kilometers to take photographs from a distance.
Regions of Mars that may be habitable for present day life are classified as "Special regions" and any parts of a spacecraft that touch such regions have to be sterilized to Viking levels of sterilization or better. So far no modern spacecraft have yet been sterilized to these levels. It is a major challenge as the heat treatment used for Viking would destroy many modern instruments. However low vapour hydrogen peroxide sterilization may be able to take the place of heat treatment - it is already approved for spacecraft use. As well as that there are emerging new ideas for sterilization that may be more effective with less damage to the spacecraft, such as use of ionized gas in vacuum conditions.
Follow the nitrogen[edit source | hide]
The best way to search for early life, as far as we can tell at present, is to search for organics. And the organics is easily confused with organics from non life processes and from space.
One of the main conclusions of Bada et al.'s white paper was that we should look for organics with nitrogen on Mars. Nitrogenous organics are likely to be rare because there are few sources of nitrogen on Mars.
This is important because nitrogen bonds are easily broken and are central to biology as we know it. So even if life on Mars is very different from Earth life, perhaps using different amino acids for instance with a different backbone from DNA, still it is likely to use nitrogen if it resembles Earth life.
Once we find these compounds, that's not enough as you also get nitrogenous organics from comets and meteorites and natural processes. We then need to search for biosignatures.
We also need to be able to drill below the surface (as ExoMars will be able to do) to the maximum depth possible. That's because our best chance of finding evidence of past life is to drill down below the surface layers damaged by ionizing radiation, ideally to ten meters depth or more (though the two meters depth of ExoMars is a good start here). Their main points are:
- Need for increasing mobility, and precision landing, supported by orbital observations, to access the many and varied habitable environments including subsurface, layered sediments, gullies and ice sheets.
- The "follow the water" strategy should now be followed by a "follow the nitrogen" phase combined with a search for biosignatures.
- The biosignature search can use exquisitely sensitive in situ electrophoresis techniques to identify and characterize and find the chirality of amines, nucleobases, polycyclics and other essential organic molecules.
- This search should include drilling to the greatest depth possible for the best chance of success for detecting biosignatures of past life on Mars
- They recommend that we should do a sample return only after we either identify biosignatures on Mars, or have exhausted all other possibilities by in situ research
Curiosity's observations of nitrous oxides, probably result of breakdown of nitrates[edit source | hide]
Curiosity has detected evidence of nitrates in both scooped wind drifted sand and samples drilled from sedimentary rocks. The results support 110–300 ppm of nitrate in the wind drifted samples, and 330–1,100 ppm nitrate in the mudstone deposits. The authors suggest that it is likely to be the result of fixation during meteorite impact or lightning associated with volcanoes in early Mars.
Curiosity's observation of complex organic compounds[edit source | hide]
Results from the Curiosity SAM instrument presented in March 2015 show presence of what may be a fatty acid molecule. Also confirm presence of chlorobenzene. Neither of these are biosignatures, for instance organisms use fatty acids to build cell membranes, but they can also have inorganic origins. But they show that complex organics can survive on the surface of Mars, so increasing the chance of later detecting microbial life on the surface if it is there.
Past missions[edit source | hide]
Viking 1 and 2 are the only successful missions to Mars to date designed to search for present day life.
The failed British mission, Beagle 2, had the search for present day life as an objective as well as past life.
Present missions[edit source | hide]
Curiosity (rover) and Opportunity (rover) are currently searching for habitable conditions with the main focus on past habitability. However they are not equipped to detect biosignatures of life, either past or present, and also were sent to sites selected with past rather than present day life as the main target.
Curiosity has some capabilities that could be of interest for life detection. It can detect isotope ratios in organics or in the methane plumes suggestive of life which could give indirect evidence of life processes as life preferentially incorporates lighter isotopes.
Curiosity also has one experiment that can potentially be used to detect chirality if it finds a potentially interesting sample to test. It has a Chirasildex column which can be used to separate out entantiomers of astrobiological significance.
Future missions[edit source | hide]
The ExoMars Trace Gas Orbiter will help with the search for trace levels of organics in the atmosphere, with sensitivity up to a thousand times greater than previous missions. Detection sensitivities are at levels of 100 parts per trillion, improved to 10 parts per trillion or better by averaging spectra which could be taken at several spectra per second. This would lead to global mapping of distribution of methane and other organics in the atmosphere which could help to pinpoint sources on the surface.
ExoMars is also designed to search for both present day and past life. It will have capabilities to test for biosignatures "in situ" on Mars. Its most interesting innovation is its capability to drill to depths of up to 2 meters which is of special interest for the search for past life. However its target regions have been selected with the search for past life as its prime objective, so it will only discover present day life if it is widespread on Mars. Its primary candidate landing site is Oxia Planum which is of interest for its multiple layers of clays which may preserve evidence of past life on Mars.
Mars 2020 is designed for sample caching for a future sample return. The payload mass is the same as for Curiosity, so to make space for the cache, as well as Moxie (an experiment in producing oxygen from the Mars atmosphere), it has a reduced mass of instruments compared with Curiosity (rover). In particular, they have removed Sample Analysis at Mars.
However, in other respects it will have increased capabilities including more capable cameras, and possibly a "helicopter scout" to search local terrain up to a kilometer away from the rover. Of special for exobiology, it will have two Raman spectrometers, first to fly to the planet (except for ExoMars if they get there first). One of them is on SHERLOC which will be positioned right next to the rock to be analysed, and uses a spot of ultraviolet laser light to micro-map minerals and organics on the samples on the scale of 50 microns. A Raman spectrometer gives information about arrangements of atoms such as a carbon atom double bonded to oxygen, but it can't detect specific molecules in the sample like SAM. Also, another significant advance, its SuperCam, replacement for the remote laser analysis instrument ChemCam on Curiosity, will not only be able to heat its target like ChemCam and analyse the plasma cloud that results. It will also have Raman and time-resolved fluorescence spectroscopy. These will enable it to map the distribution of organics on the surface of Mars at a distance, a significant advance over Curiosity which can only detect organics by heating it in its oven after sample collection. It also means it won't be confused by perchlorates destroying the organics on heat.
As for Curiosity, the target will be selected with past life as its prime objective and neither ExoMars nor Mars 2020 are sufficiently sterilized to approach and examine any possible habitats for present day life such as the RSLs
Proposals for missions[edit source | hide]
Icebreaker Life is a mission suggested by Chris McKay to search for past life preserved in ice on Mars, and present day life on Mars.
ExoLance is an ingenious proposal that uses ground penetrating "lances". Curiosity carries ballast in the form of two 75 kg tungsten weights, which it discards on arrival at Mars to help with the asymmetric trim of the aeroshell, to generate a lifting vector. That is how it manages to achieve higher precision than other missions to date. See MSL - guided entry. The idea is to put impact resistant instruments into these weights, and make them into ground penetrating "missiles" able to penetrate to a depth of a meter or so, where conditions may be more favourable for preservation of life.
NASA propose to return samples to test for biosignatures and signs of life back on Earth. Their Mars 2020 mission is designed to cache the sample, for later return to Earth by some future mission.
Instruments designed to search for present day life on Mars "in situ"[edit source | hide]
Instruments designed to search directly for this life include
Rapid non destructive sampling[edit source | hide]
- Raman spectrometry - analyses scattered light emitted by a laser on the sample. Non destructive sampling able to identify organics and signatures for life.
Detection of trace levels of organics and of chirality[edit source | hide]
- Gas chromatography - this is the idea used for the MOMA (Mars Organic Molecule Analyser). Used to analyse volatiles evolved from the soil samples in small ovens. Some of the ovens are filled with a "derivatisation agent" which can transform the chemical compounds into similar ones suitable for chiral analysis. They are then ionized and analysed with the mass spectrometer.
- UREY - designed for ExoMars under auspices of NASA but never flown because the US pulled out of the project. This uses high temperature high pressure sub critical water between 100 °C and 300 °C at 20 MPa, or about 200 atmospheres, for several minutes. Water has similar chemical properties to organic solvents in those conditions so Urey is able to study the organics relatively unmodified.
- Astrobionibbler - similar idea to UREY, smaller, later development. Able to detect a single amino acid in a gram of soil.
- Planetary In-situ Capillary Electrophersis - separates the organics by ionic mobility in sub millimeter capillaries. "Lab on a chip" with the fluid manipulations done within the chip itself.
- LDChip, and Solid3 using a collection of 450 polyclonal antibodies to detect a wide range of organics (not specific to Earth life). This instrument was tested in the Atacama desert and was able to detect a layer of previously undiscovered life at a depth of 2 meters below the surface in the hyper-arid core of the desert. As the "Life Marker Chip" it was selected for ExoMars but later descoped.
Direct search for DNA[edit source | hide]
Electron microscope[edit source | hide]
- Miniaturized Variable Pressure Scanning Electron Microscope (MVP-SEM)
Search for life directly by checking for metabolic reactions[edit source | hide]
These can detect life even if it doesn't use any recognized form of conventional life chemistry. But requires the life to be "cultivable" in vitro when it meets appropriate conditions for growth.
- Microbial fuel cells, test for redox reactions directly by measuring electrons and protons they liberate. Sensitive to small numbers of microbes and could detect life even if not based on carbon or any form of conventional chemistry we know of.
- Chirality version of the Viking Labeled Release. For carbon based life which produces gases such as methane or carbon dioxide when fed amino acids, but doesn't need to be DNA based life.
See also[edit source | hide]
[edit source | hide]
- Three days long conference on the subject in 2013 The Present-Day Habitability of Mars 2013 under the auspices of the UCLA Institute for Planets and Exoplanets - with video archived for all the talks.
References[edit source | hide]
- Phoenix Mars Lander Finds Surprises About Planet’s Watery Past University of Arizona news, By Daniel Stolte, University Communications, and NASA's Jet Propulsion Laboratory | September 9, 2010
- First liquid water may have been spotted on Mars, New Scientist, February 2009 by David Shiga
- Martian Life Could Have Evaded Detection by Viking Landers Ker Than, Staff Writer | October 24, 2006 05:56pm, Space.com
- Periodic Analysis of the Viking Lander Labeled Release Experiment, Proc. SPIE 4495, Instruments, Methods, and Missions for Astrobiology IV, 96 (February 6, 2002); doi:10.1117/12.454748
"Did Viking Lander biology experiments detect life on Mars? ... Recent observations of circadian rhythmicity in microorganisms and entrainment of terrestrial circadian rhythms by low amplitude temperature cycles argue that a Martian circadian rhythm in the LR experiment may constitute a biosignature."
- Levin, G.V. and Straat, P.A., 2016. The case for extant life on Mars and its possible detection by the Viking labeled release experiment. Astrobiology, 16(10), pp.798-810.
"It is concluded that extant life is a strong possibility, that abiotic interpretations of the LR data are not conclusive, and that, even setting our conclusion aside, biology should still be considered as an explanation for the LR experiment. Because of possible contamination of Mars by terrestrial microbes after Viking, we note that the LR data are the only data we will ever have on biologically pristine martian samples"
- Bianciardi, Giorgio; Miller, Joseph D.; Straat, Patricia Ann; Levin, Gilbert V. (March 2012). "Complexity Analysis of the Viking Labeled Release Experiments" (PDF). IJASS. 13 (1): 14–26. Bibcode:2012IJASS..13...14B. doi:10.5139/IJASS.2012.13.1.14. Retrieved 2012-04-15.
These analyses support the interpretation that the Viking LR experiment did detect extant microbial life on Mars
- Plaxco, Kevin W.; Gross, Michael (2011-08-12). Astrobiology: A Brief Introduction. JHU Press. pp. 285–286. ISBN 978-1-4214-0194-2. Retrieved 2013-07-16.
- How Habitable Is Mars? A New View of the Viking Experiments By Elizabeth Howell -Astrobiology Magazine (NASA) Nov 21, 2013
- Levin, G. V.; Straat, P. A. (1976). "Viking Labeled Release Biology Experiment: Interim Results". Science. 194 (4271): 1322–1329. Bibcode:1976Sci...194.1322L. doi:10.1126/science.194.4271.1322. PMID 17797094.
- "Extracts from "Making a Splash on Mars"" (PDF).
- Martínez, G. M.; Renno, N. O. (2013). "Water and Brines on Mars: Current Evidence and Implications for MSL". Space Science Reviews. 175 (1–4): 29–51. Bibcode:2013SSRv..175...29M. doi:10.1007/s11214-012-9956-3. ISSN 0038-6308.
- NASA Mars Orbiters See Clues to Possible Water Flows, Astrobiology Magazine (NASA), Feb 12, 2014
- Water seems to flow freely on Mars, Nature news, Maggie McKee 10 December 2013
- Kereszturi, A., et al. "Analysis of possible interfacial water driven seepages on Mars", Lunar and Planetary Science Conference. Vol. 39. 2008.
- Möhlmann, Diedrich T.F. (2010). "Temporary liquid water in upper snow/ice sub-surfaces on Mars?". Icarus. 207 (1): 140–148. Bibcode:2010Icar..207..140M. doi:10.1016/j.icarus.2009.11.013. ISSN 0019-1035.
- Rincon Science editor, Paul (April 13, 2015). "Evidence of liquid water found on Mars". BBC News website.
- Liquid Water from Ice and Salt on Mars, Aaron L. Gronstal -Astrobiology Magazine (NASA), Jul 3, 2014
- Surviving the conditions on Mars DLR, 26 April 2012
- Starting conditions for hydrothermal systems underneath Martian craters: Hydrocode modeling Pierazzo, E., Artemieva, N.A., and Ivanov, B.A., 2005, from Large Meteorite Impacts III, Issue 384, p 444 edited by Thomas Kenkmann, Friedrich Hörz, Alexander Deutsch Geological Society of America, 1 Jan 2005 (pdf, earlier version with colour graphics)
- NASA (December 19, 2014). "NASA, Planetary Scientists Find Meteoritic Evidence of Mars Water Reservoir".
- Lasue, Jeremie, et al. "Quantitative assessments of the martian hydrosphere." Archived 2017-03-22 at the Wayback Machine. Space Science Reviews 174.1-4 (2013): 155-212.
- Michalski, Joseph R., et al. "Groundwater activity on Mars and implications for a deep biosphere." Nature Geoscience 6.2 (2013): 133-138.
- Present-day Uninhabited Habitats on Mars, Charles S. Cockell
- Planetary Exploration and Science: Recent Results and Advances, Antonio de Morais M. Teles, page 153, 27 Nov 2014
- Habitability of other planets and satellites - Habitability and Survival, Francis Westall, page 192, 30 Jul 2013
"This presupposes that the ephemeral surface habitats could be colonized by viable life forms, that is, that a subsurface reservoir exists in which microbes could continue to metabolize and that, as noted above, the viable microbes could be transported into the short-lived habitat.... Although there are a large number of constraints on the continued survival of life in the subsurface of Mars, the astonishing biomass in the subsurface of Earth suggests that this scenario as a real possibility."
- Morozova, Daria; Möhlmann, Diedrich; Wagner, Dirk (2006). "Survival of Methanogenic Archaea from Siberian Permafrost under Simulated Martian Thermal Conditions" (PDF). Origins of Life and Evolution of Biospheres. 37 (2): 189–200. doi:10.1007/s11084-006-9024-7. ISSN 0169-6149.
The observation of high survival rates of methanogens under simulated Martian conditions supports the possibility that microorganisms similar to the isolates from Siberian permafrost could also exist in the Martian permafrost.
- Crisler, J.D.; Newville, T.M.; Chen, F.; Clark, B.C.; Schneegurt, M.A. (2012). "Bacterial Growth at the High Concentrations of Magnesium Sulfate Found in Martian Soils". Astrobiology. 12 (2): 98–106. doi:10.1089/ast.2011.0720. ISSN 1531-1074. PMC .
Our results indicate that terrestrial microbes might survive under the high-salt, low-temperature, anaerobic conditions on Mars and present significant potential for forward contamination. Stringent planetary protection requirements are needed for future life-detection missions to Mars
- Kilmer, Brian R.; Eberl, Timothy C.; Cunderla, Brent; Chen, Fei; Clark, Benton C.; Schneegurt, Mark A. (2014). "Molecular and phenetic characterization of the bacterial assemblage of Hot Lake, WA, an environment with high concentrations of magnesium sulphate, and its relevance to Mars". International Journal of Astrobiology. 13 (01): 69–80. Bibcode:2014IJAsB..13...69K. doi:10.1017/S1473550413000268. ISSN 1473-5504. PMC . PMID 24748851.
- Rummel, J.D., Beaty, D.W., Jones, M.A., Bakermans, C., Barlow, N.G., Boston, P.J., Chevrier, V.F., Clark, B.C., de Vera, J.P.P., Gough, R.V. and Hallsworth, J.E., 2014. A new analysis of Mars “special regions”: findings of the second MEPAG Special Regions Science Analysis Group (SR-SAG2)..
"Claims that reducing planetary protection requirements wouldn't be harmful, because Earth life can't grow on Mars, may be reassuring as opinion, but the facts are that we keep discovering life growing in extreme conditions on Earth that resemble conditions on Mars. We also keep discovering conditions on Mars that are more similar—though perhaps only at microbial scales—to inhabited environments on Earth, which is where the concept of Special Regions initially came from."
- Davila, A.F., Skidmore, M., Fairén, A.G., Cockell, C. and Schulze-Makuch, D., 2010. New priorities in the robotic exploration of Mars: the case for in situ search for extant life. Astrobiology, 10(7), pp.705-710.
"We argue that the strategy for Mars exploration should center on the search for extant life. By extant life, we mean life that is active today or was active during the recent geological past and is now dormant. As we discuss below, the immediate strategy for Mars exploration cannot focus only on past life based on the result of the Viking missions, particularly given that recent analyses call for a re-evaluation of some of these results. It also cannot be based on the astsumption that the surface of Mars is uniformly prohibitive for extant life, since research contributed in the past 30 years in extreme environments on EArth has shown that life is possible under extremes of cold and dryness."
- Fairén, A.G., Parro, V., Schulze-Makuch, D. and Whyte, L., 2017. Searching for life on Mars before it is too late. Astrobiology, 17(10), pp.962-970.
"The case of ExoMars is particularly dramatic as the first priority of the rover is to search for signs of past and present life on Mars ... however, it has been explicitly banned to go to Special Regions because it will not comply with the minimum cleanliness requirements. As a consequence, the billion-dollar life-seeking mission ExoMars will be allowed to search for life everywhere on Mars, except in the very places where we suspect that life may exist."
- de Vera, Jean-Pierre; Schulze-Makuch, Dirk; Khan, Afshin; Lorek, Andreas; Koncz, Alexander; Möhlmann, Diedrich; Spohn, Tilman (2014). "Adaptation of an Antarctic lichen to Martian niche conditions can occur within 34 days". Planetary and Space Science. 98: 182–190. doi:10.1016/j.pss.2013.07.014. ISSN 0032-0633.
This work strongly supports the interconnected notions (i) that terrestrial life most likely can adapt physiologically to live on Mars (hence justifying stringent measures to prevent human activities from contaminating / infecting Mars with terrestrial organisms); (ii) that in searching for extant life on Mars we should focus on "protected putative habitats"; and (ii) that early-originating (Noachian period) indigenous Martian life might still survive in such micro-niches despite Mars' cooling and drying during the last 4 billion years
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The results achieved from our study led to the conclusion that black microcolonial fungi can survive in Mars environment.
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transcript from 2 minutes into the video onwards, from Nilton Renno video (youtube)
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- Donald M. Hassler, Cary Zeitlin, Robert F. Wimmer-Schweingruber, Bent Ehresmann, Scot Rafkin, Jennifer L. Eigenbrode, David E. Brinza, Gerald Weigle, Stephan Böttcher, Eckart Böhm, Soenke Burmeister, Jingnan Guo, Jan Köhler, Cesar Martin, Guenther Reitz, Francis A. Cucinotta, Myung-Hee Kim, David Grinspoon, Mark A. Bullock, Arik Posner, Javier Gómez-Elvira, Ashwin Vasavada, and John P. Grotzinger, and the MSL Science Team (12 November 2013). "Mars' Surface Radiation Environment Measured with the Mars Science Laboratory's Curiosity Rover" (PDF). Science: 8.
- Joanna Carver and Victoria Jaggard (21 November 2012). "Mars is safe from radiation – but the trip there isn't". New Scientist.
- Redox chemistry - defines pH and Eh
- Mars Sprinkled with Salty Mysteries by Andrea Thompson, Senior Writer, Space.com, April 14, 2009
- Oren, Aharon; Elevi Bardavid, Rahel; Mana, Lily (2013). "Perchlorate and halophilic prokaryotes: implications for possible halophilic life on Mars". Extremophiles. 18 (1): 75–80. doi:10.1007/s00792-013-0594-9. ISSN 1431-0651. PMID 24150694.
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- Minkel, JR (August 5, 2008). "NASA Says Perchlorate Does Not Rule Out Life on Mars - Unexpected chemical in Martian soil is a food source for some Earthly microbes". Scientific American.
- CHANG, KENNETH (October 5, 2015). "Mars Is Pretty Clean. Her Job at NASA Is to Keep It That Way".
- Chang, Kenneth (October 5, 2015). "Mars Is Pretty Clean. Her Job at NASA Is to Keep It That Way". New York Times.
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- McKay, Christopher P. "An origin of life on Mars." Cold Spring Harbor perspectives in biology 2.4 (2010): a003509.
- Rummel, John D.; Beaty, David W.; Jones, Melissa A.; Bakermans, Corien; Barlow, Nadine G.; Boston, Penelope J.; Chevrier, Vincent F.; Clark, Benton C.; de Vera, Jean-Pierre P.; Gough, Raina V.; Hallsworth, John E.; Head, James W.; Hipkin, Victoria J.; Kieft, Thomas L.; McEwen, Alfred S.; Mellon, Michael T.; Mikucki, Jill A.; Nicholson, Wayne L.; Omelon, Christopher R.; Peterson, Ronald; Roden, Eric E.; Sherwood Lollar, Barbara; Tanaka, Kenneth L.; Viola, Donna; Wray, James J. (2014). "A New Analysis of Mars "Special Regions": Findings of the Second MEPAG Special Regions Science Analysis Group (SR-SAG2)". Astrobiology. 14 (11): 887–968. Bibcode:2014AsBio..14..887R. doi:10.1089/ast.2014.1227. ISSN 1531-1074.
- Carnobacterium on Microbewiki
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- Carbon monoxide as a metabolic energy source for extremely halophilic microbes: Implications for microbial activity in Mars regolith Gary M. King, PNAS March 23, 2015, doi:10.1073/pnas.1424989112
- Nicholson, Wayne, et al. "Isolation of bacteria from Siberian permafrost capable of growing under simulated Mars atmospheric pressure and composition." 40th COSPAR Scientific Assembly. Held 2–10 August 2014, in Moscow, Russia, Abstract F3. 3-10-14.. Vol. 40. 2014.
- Tremblay, Pier-Luc; Aklujkar, Muktak; Leang, Ching; Nevin, Kelly P.; Lovley, Derek (2012). "A genetic system for Geobacter metallireducens: role of the flagellin and pilin in the reduction of Fe(III) oxide". Environmental Microbiology Reports. 4 (1): 82–88. doi:10.1111/j.1758-2229.2011.00305.x. ISSN 1758-2229.
- Geobacter metallireducens on the Microbe wiki
- Circinaria gyrosa, a new astrobiological model system for studying the effects of heavy ion irradiation, María Luisa Martín; Ralf Moeller; Rosa De la Torre Noetzel, ; M. Marina Raguse, 40th COSPAR Scientific Assembly. Held 2–10 August 2014, in Moscow, Russia, Abstract F3.3-9-14. Bibliographic Code: 2014cosp...40E2015M
- Survival of the lichen model system Circinaria gyrosa before flight to the ISS (EXPOSE R2 mission), Rosa De la Torre Noetzel, Publication: 40th COSPAR Scientific Assembly. Held 2–10 August 2014, in Moscow, Russia, Abstract F3.1-9-14. Bibliographic Code: 2014cosp...40E.650D
- Desulforudis audaxviator Daniel Roush
- Desulforudis audaxviator on Microbe Wiki
- Subterranean worms from hell- New species of nematode discovered more than a kilometre underground, Nadia Drake June 2011, Nature, doi:10.1038/news.2011.342
- "Researchers have found in the deep ocean the first-known kinds of multicellular organisms, dubbed Loricifera, that live completely oxygen-free" Multicellular Life Found That Doesn't Need Oxygen, Cynthia Graber, Scientific American, April 9, 2010
- Gronstal, Aaron L (Jul 31, 2014). "BIOMEX: Exploring Mars in Low Earth Orbit". Astrobiology Magazine (NASA).
- Rabbow, E., Rettberg, P., Parpart, A., Panitz, C., Schulte, W., Molter, F., Jaramillo, E., Demets, R., Weiß, P. and Willnecker, R., 2017. EXPOSE-R2: the astrobiological ESA mission on board of the international space station. Frontiers in microbiology, 8, p.1533.
- "Potsdam algae in space fitness tests". biotechnologie.de.
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- The Expose-R2 mission: Astrobiology and astrochemistry in low Earth orbit, Biotechnology Summer School René Demets Project Scientist Astrobiology ESA-ESTEC (HSO-USB) Tuesday 26 August 2014
- The Expose-R2 mission: Astrobiology and astrochemistry in low Earth orbit, René Demets, ESA (powerpoint)
- "BIOMEX: Biology and Mars Experiment". DLR.
- BIOMEX on EXPOSE-R2: First results on the preservation of Raman biosignatures after space exposure. Baqué, Mickael; Böttger, Ute; Leya, Thomas; de Vera, Jean-Pierre Paul. 19th EGU General Assembly, EGU2017, proceedings from the conference held 23–28 April 2017 in Vienna, Austria., p.3697.
- Endurance of desert-cyanobacteria biofilms to space and simulated Mars conditions during the EXPOSE-R2 space mission. Billi, D. and Verseux, C. and Rabbow, E. and Rettberg, P. DLR Portal. EANA 2017, 14.-17. August, 2017, Aarhus, Denmark.
- Rabbow, Elke; Rettberg, Petra; Parpart, Andre; Panitz, Corinna; Schulte, Wolfgang; Molter, Ferdinand; Jaramillo, Esther; Demets, René; Weiß, Peter; Willnecker, Rainer (2017). "EXPOSE-R2: The Astrobiological ESA Mission on Board of the International Space Station". Frontiers in Microbiology. 8. doi:10.3389/fmicb.2017.01533.
- Cockell, CS (2014). "Trajectories of martian habitability". Astrobiology. 14: 182–203. Bibcode:2014AsBio..14..182C. doi:10.1089/ast.2013.1106. PMC . PMID 24506485.
- Cockell, Charles S. (2012). "Uninhabited habitats on Mars". Icarus. 217: 184–193. Bibcode:2012Icar..217..184C. doi:10.1016/j.icarus.2011.10.025.
- McKay, Chris P. (2004). "What Is Life—and How Do We Search for It in Other Worlds?". PLoS Biology. 2 (9): e302. doi:10.1371/journal.pbio.0020302. ISSN 1544-9173.
- "NASA Weighs Use of Rover to Image Potential Mars Water Sites". NASA (JPL) Press release. June 24, 2016.
- Could Ionized Gas Do A Better Job of Sterilizing Spacecraft?, Elizabeth Howell - Feb 23, 2015, Astrobiology Magazine (NASA)
- Jeffrey L. Bada, Andrew D. Aubrey, Frank J. Grunthaner, Michael Hecht, Richard Quinn, Richard Mathies, Aaron Zent, John H. Chalmers Seeking signs of life on mars: in situ investigations as prerequisites to sample return missions Independent Contribution to the Mars Decadal Survey Panel
- Evidence for indigenous nitrogen in sedimentary and aeolian deposits from the Curiosity rover investigations at Gale crater, Mars Jennifer C. Stern, PNAS March 23, 2015, doi:10.1073/pnas.1420932112
- Curiosity Mars rover detects 'useful nitrogen', BBC News, March 2015
- More Ingredients for Life Identified on Mars by Mike Wall, Space.com Senior Writer, space.com, March 23, 2015
- NASA's Curiosity rover finds fatty acids on Mars, New Scientist, 25 March 2015
- Francois, Pascaline, et al. "The Sample Analysis At Mars Gas Chromatograph (sam-gc) Ability To Detect Organic Molecules At The Mars Surface." AAS/Division for Planetary Sciences Meeting Abstracts. Vol. 44. 2012.
- Vandaele, A. C., et al. "NOMAD, a spectrometer suite for Nadir and Solar occultation observations on the exomars trace gas orbiter." Fourth International Workshop on the Mars Atmosphere: Modelling and Observation, Paris, France. 2011.
- "LANDING SITE RECOMMENDED FOR EXOMARS 2018". ESA. 21 October 2015.
- Hand, Eric (July 31, 2014). "NASA's Mars 2020 rover to feature lean, nimble science payload". Science Insider.
- Chris Gebhardt (October 11, 2016). "Mars 2020 rover receives upgraded eyesight for tricky skycrane landing". nasaspaceflight.com.
- "SHERLOC to Micro-Map Mars Minerals and Carbon Rings". Future rover plans (NASA). July 31, 2014.
- Kane, Van (August 6, 2014). "Mars 2020 Instruments – A Plan for Sample Return".
- Wall (Senior science writer), Mike (September 15, 2014). "Life-Hunting Mars Mission Idea Makes Progress, But Needs Cash". Space.com.
- Foust, Jeff (5 May 2014). "Mars missions on the cheap". The Space Review. Retrieved 2014-05-06.
- "ExoLance". Explore Mars Inc. 2014. Retrieved 2014-05-06.
- Koebler, Jason (24 April 2014). "Blasting Mars with Missiles Is the Latest Hope for Finding Martian Life". Motherboard. Retrieved 2014-05-06.
- Chris Carberry and Blake Ortner (August 4, 2014). "Searching for Subsurface Life on Mars".
- "THE EXOMARS ROVER INSTRUMENT SUITE - RAMAN SPECTROMETER". ESA.
- ESA. "MOMA - MARS ORGANICS MOLECULE ANALYSER". ESA.
- Andrew D. Aubrey, John H. Chalmers, Jeffrey L. Bada, Frank J. Grunthaner, Xenia Amashukeli, Peter Willis, Alison M. Skelley, Richard A. Mathies, Richard C. Quinn, Aaron P. Zent, Pascale Ehrenfreund, Ron Amundson, Daniel P. Glavin, Oliver Botta, Laurence Barron, Diana L. Blaney, Benton C. Clark, Max Coleman, Beda A. Hofmann, Jean-Luc Josset, Petra Rettberg, Sally Ride, François Robert, Mark A. Sephton, and Albert Yen1 The Urey Instrument: An Advanced In Situ Organic and Oxidant Detector for Mars Exploration ASTROBIOLOGY Volume 8, Number 3, 2008
- J.L. Bada ·P. Ehrenfreund ·F. Grunthaner ·D. Blaney ·M. Coleman · A. Farrington ·A. Yen ·R. Mathies·R. Amudson ·R. Quinn ·A. Zent·S. Ride · L. Barron ·O. Botta ·B. Clark ·D. Glavin ·B. Hofmann · J.L. Josset·P. Rettberg · F. Robert ·M. Sephton Urey: Mars Organic and Oxidant Detector Space Sci Rev (2008) 135: 269–279
- Searching for Organics in a Nibble of Soil, Michael Schirber, Astrobiology Magazine (NASA), 18th February 2013
- Willis, P. A., Stockton, A. M., Mora, M. F., Cable, M. L., Bramall, N. E., Jensen, E. C., ... & Mathies, R. A. (2012). Planetary In Situ Capillary Electrophoresis System (PISCES). LPI Contributions, 1683, 1038.
- THE SOLID3 ("SIGNS OF LIFE DETECTOR") INSTRUMENT: AN ANTIBODY MICROARRAYBASED BIOSENSOR FOR PLANETARY EXPLORATION. V. Parro , L. A. Rivas , E. Sebastián , Y. Blanco , J. A. Rodríguez-Manfredi , G. de Diego-Castilla , M. Moreno-Paz , M. García-Villadangos , C. Compostizo , P. L. Herrero , A. García-Marín , J. Martín-Soler , J. Romeral , P. Cruz-Gil , O. Prieto-Ballesteros , and J. Gómez-Elvira, Concepts and Approaches for Mars Exploration (2012)
- Microbial oasis discovered beneath the Atacama Desert, PUBLIC RELEASE: 16-FEB-2012, FECYT - SPANISH FOUNDATION FOR SCIENCE AND TECHNOLOGY
- Parro, Victor; de Diego-Castilla, Graciela; Moreno-Paz, Mercedes; Blanco, Yolanda; Cruz-Gil, Patricia; Rodríguez-Manfredi, José A.; Fernández-Remolar, David; Gómez, Felipe; Gómez, Manuel J.; Rivas, Luis A.; Demergasso, Cecilia; Echeverría, Alex; Urtuvia, Viviana N.; Ruiz-Bermejo, Marta; García-Villadangos, Miriam; Postigo, Marina; Sánchez-Román, Mónica; Chong-Díaz, Guillermo; Gómez-Elvira, Javier (2011). "A Microbial Oasis in the Hypersaline Atacama Subsurface Discovered by a Life Detector Chip: Implications for the Search for Life on Mars". Astrobiology. 11 (10): 969–996. Bibcode:2011AsBio..11..969P. doi:10.1089/ast.2011.0654. ISSN 1531-1074. PMC . PMID 22149750.
- s. M. R. Sims, D. C. Cullen, M. A. Sephton, C. Bulloch, G. Borst, H. Leeuwis, A. Norfini, J. Brucato, N. Holm, A. Steele, P. Ehrenfreund. "The Life Marker Chip (LMC) instrument - Antibody-based detection of organic molecules and biomarkers in Martian samples". Concepts and Approaches for Mars Exploration (2012).
- Mars Sample Return Mission? Naaah… Just Beam Back Martian DNA
- Biomedicine News Genome Hunters Go After Martian DNA
- Researchers Design a DNA Sequencing Microchip for Detecting Life on Mars Science Tech Daily, July 9, 2013
- Radiation Resistance of Sequencing Chips for in situ Life Detection Christopher E. Carr, Holli Rowedder, Clarissa S. Lui, Ilya Zlatkovsky, Chris W. Papalias, Jarie Bolander, Jason W. Myers, James Bustillo, Jonathan M. Rothberg, Maria T. Zuber, and Gary Ruvkun. Astrobiology. June 2013, 13(6) 560-569. doi:10.1089/ast.2012.0923
- Gaskin, J.A.; Jerman, G.; Gregory, D.; Sampson, A.R., Miniature Variable Pressure Scanning Electron Microscope for in-situ imaging & chemical analysis Aerospace Conference, 2012 IEEE, vol., no., pp.1,10, 3–10 March 2012 doi: 10.1109/AERO.2012.6187064
- Abrevaya, Ximena C., Pablo JD Mauas, and Eduardo Cortón. "Microbial fuel cells applied to the metabolically based detection of extraterrestrial life." Astrobiology 10.10 (2010): 965-971.
- A. D. Anbar1 and G. V. Levin A CHIRAL LABELED RELEASE INSTRUMENT FOR IN SITU DETECTION OF EXTANT LIFE., Concepts and Approaches for Mars Exploration (2012) | 0.880185 | 3.525277 |
This is Gault, an asteroid that is slowly crumbling as it hurtles through space, trailing two enormous, comet-like tails of debris. That longer one is some half a million miles long. Scientists think the mini-planet is being destroyed by a mechanism called YORP: Basically, that’s where sunlight warms the surface of an asteroid. As that thermal energy then radiates back into space, it works almost like tiny thrusters, causing the rock to spin faster and faster—until pieces begin to fly off into space.
Clouds swirl and dance around themselves above the Indian Ocean in this photo taken by an astronaut on the International Space Station last month. Toward the upper left of the photo, the thin, bright blue veneer of our atmosphere is what contains us and separates us from space.
This long, colorful photo shows a region on Mars called Meridiani Planum, the home and final resting place of NASA’s Opportunity rover. The rover spent 15 years exploring the Red Planet, studying rocks and even detecting the first evidence of water. But it was snuffed out by the worst dust storm to ever hit Mars. The end of the mission was sad, but the fact that it lasted so long was evidence of how well engineered Oppy was—it was only supposed to last three months!
This image is based on information from the European Space Agency’s Mars Express Satellite and digital models. It’s a region called Chalcoporos Rupes, and it’s covered in dust and craters. You can also see the dark tracks left over from dust devils that sweep through the area. This oblique angle almost makes it feel as though we have a jet pack on and are slowly descending to the surface. Watch out for dust devils!
This photo shows a flock of cosmic ducks, or at least that’s what NASA sees. This is Messier 11, but it’s also known as the Wild Duck Cluster, because it is said to resemble a flock of wild ducks. Space ducks, can you see it? Scientists think that Messier 11 formed over 200 million years ago and is what’s known as a compact open cluster. If you look at the center of the photo you’ll see a lot of bright blue “ducks.” Those are younger stars characterized by the hot gas they give off.
NASA combined data from three telescopes to create this photo showing a massive stellar nursery called W51. See all those bright regions? Massive stars are forming there. One of the new stars just discovered is nearly 100 times more massive than our own sun. By studying star-forming regions like this, scientists are able to determine the age of the clouds of gas and dust that these stars are born into and better piece together how star formation works. | 0.876814 | 3.483726 |
The now recognized extensive existence of life on earth very shortly after the destructive bombardment of the earth's surface by early solar system debris has stimulated inquiry into possible exogenous sources of prebiotic molecules from space as well as intensified studies of the early earth's atmosphere.
The chapters in The Chemistry of Life's Origin cover the possible sources of prebiotic molecules and avenues by which life could have evolved, starting from the birth and evolution of the solar system. The relevance of the classic experiments by Stanley Miller on the formation of life's building blocks on an early earth is reexamined. The role of chemistry in space is covered by chapters on interstellar dust, and meteorites to which experimental as well as theoretical investigations have been directed. In various chapters the existence of amino acids as well as other prebiotic molecules in meteorites is clearly established and inferred for interstellar dust and comets. Theories of molecular synthesis in the solar nebula are considered. Extensive coverage is given to the physical conditions and to prebiotic systems on the early earth. Possible pathways to life on an early Mars and the possible messages to be obtained by space exploration are discussed. Questions of effects of clays and of chirality on early chemical evolution are discussed. Recent ideas on the RNA world as the precursor to life are reviewed. The open-endedness of the study of life's origins and the need to investigate whether the prebiotic building blocks formed in outer space or on the earth is emphasized.
A good deal of The Chemistry of Life's Origin is suitable to graduate students.
- Interstellar dust evolution: a reservoir of prebiotic molecules, J.M. Greenberg, C.X. Mendoza-Gomez
- Laboratory simulations of grain icy mantles processing by cosmic rays, V. Pirronello
- Physics and chemistry of protoplanetary accretion disks, W.J. Duschl
- Chemistry of the solar nebula, B. Fegley, Jr.
- Early evolution of the atmosphere and ocean, J.F. Kasting
- Origin and evolution of Martian atmosphere and climate and possible exobiological experiments, L.M. Mukhin
- The possible pathways of the synthesis of precursors on the early earth, L.M. Mukhin, M.V. Gerasimov
- Physical and chemical composition of comets - from interstellar space to the earth, J.M. Greenberg
- Organic matter in meteorites - molecular and isotopic analyses of the Murchison meteorite, J.R. Cronin, S. Chang
- Prebiotic synthesis in planetary environments, S. Chang
- Prebiotic synthesis on minerals - RNA oligomer formation, J.P. Ferris
- Biology and theory - RNA and the origin of life, A.W. Schwartz
- Chirality and the origins of life, A. Brack
- Early proteins, A. Brack
- The beginnings of life on earth - evidence from the geological record, M. Schidlowski | 0.854644 | 3.744259 |
Earth's magnetic field
The Earth’s magnetic field is created by the rotation of the Earth and Earth's core. It shields the Earth against harmful particles in space. The field is unstable and has changed often in the history of the Earth. As the Earth spins the two parts of the core move at different speeds and this is thought to generate the magnetic field around the Earth as though it had a large bar magnet inside it.
The magnetic field creates magnetic poles that are near the geographical poles. A compass uses the geomagnetic field to find directions. Many migratory animals also use the field when they travel long distances each spring and fall. The magnetic poles will trade places during a magnetic reversal.
The Earth’s geomagnetic field is created because of two things. The convective motions in the liquid conducting core inside the center of the Earth are important for making the magnetic field. When the convective motions occur with the electrical currents around the Earth, the magnetic field is created. The Earth’s rotation is what keeps the magnetic field up. The interaction between the convective motions and the electrical currents creates a dynamo effect.
The intensity of the magnetic field is greatest near the magnetic poles where it is vertical. The intensity of the field is weakest near the equator where it is horizontal. The magnetic field’s intensity is measured in gauss.
The magnetic field has decreased in strength through recent years. In the past twenty-two years, the field has decreased its strength 1.7%, on average. In some areas of the field, the strength has decreased up to 10%. The fast strength decrease of the field is a sign that the magnetic field might be reversing. The reversal might happen in the next few thousand years. It has been shown that the movement of the magnetic poles is related to the decreasing strength of the magnetic field.
A geomagnetic reversal is when the north magnetic pole and south magnetic pole trade places. This has happened a few times in the history of the Earth. The magnetic reversal happens after the strength of the field reaches zero. When the strength begins to increase again, it will increase in the opposite direction, causing a reversal of the magnetic poles. The time it takes the magnetic field to undergo a reversal is unknown, but can last up to ten thousand years. The Earth’s magnetic reversals are recorded in rocks, especially in basalt. Scientists believed that the last geomagnetic reversal occurred 780,000 years ago.
The magnetosphere is created by the magnetic field. It is the area around the Earth that acts as a shield against the harmful particles in solar wind. The magnetosphere has many different layers and structures, and solar wind shapes each of these layers. The interaction of solar wind and the magnetosphere also causes the Northern and Southern Lights to appear. The magnetosphere is very important in protecting the Earth against solar storms which increase solar wind activity. Solar storms can cause geomagnetic storms which sometimes have serious affects on the Earth.
The areas in between the north and south magnetic poles are the magnetic field lines. These lines leave the Earth from the vertical point of the South and reenters through the vertical point of the North. These two vertical points are called magnetic dip poles. The magnetic dip poles are commonly referred to as the magnetic poles. The magnetic poles intersect the earth at two points. The north magnetic pole intersects the Earth at 78.3 N latitude and 100 W longitude. This places the north magnetic pole in the Arctic Circle. The south magnetic pole intersects the Earth at 78.3 S latitude and 142 E longitude. This places the south magnetic pole in Antarctica. The magnetic poles are also where the magnetic fields are the strongest.
Earth's magnetic polesEdit
Like other magnetic fields, the Earth's magnetic field has magnetic poles.
The North Magnetic Pole is the point on the surface of Earth's northern hemisphere where the planet's magnetic field points vertically downwards. There is only one place where this occurs, near to (but distinct from) the Geographic North Pole.
Its southern hemisphere counterpart is the South Magnetic Pole. Since the Earth's magnetic field is not exactly symmetrical, a line drawn from one to the other does not pass through the geometric centre of the Earth.
The North Magnetic Pole moves over time due to magnetic changes in the Earth's core. In 2001, it was near Ellesmere Island in northern Canada at . As of 2015, the pole is thought to have moved east beyond the Canadian Arctic territorial claim to .
The Earth's North and South Magnetic Poles are also known as Magnetic Dip Poles, referring to the vertical "dip" of the magnetic field lines at those points.
Some migratory animals know their locations by the intensity of the field. They know the time because of circadian rhythms the field produces. Migratory animals are born with a magnetic map in their head that allows them to migrate great distances safely. Their ability to sense the magnetic field is because of magnetic particles. Other animals have a chemical compass based on a radical pair mechanism.
|Wikimedia Commons has media related to Earth's magnetic field.|
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- Dergachev V.A.; et al. (2012). "Impact of the geomagnetic field and solar radiation on climate change". Geomagnetism and Aeronomy. 52 (8): 959–976.
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- Dergachev V.A.; et al. (2011). "The connection between cosmic rays and changes in the geomagnetic field and the Earth's climate". Bulletin of the Russian Academy of Sciences:Physics. 75 (6): 847–850.
- Mikhailova G.A. & Smirnov S.E. (2011). "Effects of geomagnetic disturbances in the near Earth's atmosphere and possible biophysical mechanism of their influence on the human cardiovascular system". Izvestiya, Atmospheric and Oceanic Physics. 47 (7): 805–818.
- Bertolotti, Mario (2012). "The Earth's magnetic field and the geomagnetic effects". Celestial messengers: cosmic rays: the story of a scientific adventure. Astronomers' Universe. Springer. pp. 75–103. ISBN 978-3-642-28370-3.
- Merrill, Ronald T.; McElhinny, Michael W.; McFadden, Phillip L. (1996). "Chapter 8". The magnetic field of the earth: paleomagnetism, the core, and the deep mantle. Academic Pres]. ISBN 978-0-12-491246-5.
- World Data Center for Geomagnetism, Kyoto. "Magnetic North, Geomagnetic and Magnetic Poles". Retrieved 2012-07-03.
- "The Magnetic North Pole". Ocean bottom magnetology laboratory. Woods Hole Oceanographic Institution. Retrieved June 2012. Check date values in:
- Scott, Rebecca, Robert Marsh, and Graeme C. Hays (2012). "A little movement orientated to the geomagnetic field makes a big difference in strong flows". Marine Biology. 159 (3): 481–488.
|url=(help)CS1 maint: multiple names: authors list (link)
- Wiltschicko, Wolfgang and Roswitha Witschko (2005). "Magnetic orientation and magnetoreception in birds and other animals". Journal of Comparative Physiology. 191 (8): 675–693.
- Gould J.L. (1984). "Magnetic field sensitivity in animals". Annual Review of Physiology. 46: 585–598.
- Lehikoinen, Aleksi and Kim Jaatinen (2011). "Delayed Autumn migration in northern european waterfowl" (PDF). Journal of Ornithology. 153 (2): 563–570. Retrieved 26 February 2013. | 0.809946 | 3.477528 |
Ever since the MESSENGER spacecraft entered orbit around Mercury in 2011, and indeed even since Mariner 10‘s flyby in 1974, peculiar “dark spots” observed on the planet’s surface have intrigued scientists as to their composition and origin. Now, thanks to high-resolution spectral data acquired by MESSENGER during the last few months of its mission, researchers have confirmed that Mercury’s dark spots contain a form of carbon called graphite, excavated from the planet’s original, ancient crust.
Researchers from the Carnegie Institution have found that water is present in surprisingly Earthlike amounts within Mars’ mantle, based on studies of meteorites that originate from the Red Planet. The findings offer insight as to how Martian water may have once made its way to the planet’s surface, as well as what may lie within other terrestrial worlds.
Earth has water on its surface (obviously) and also within its crust and mantle. The water content of Earth’s upper mantle — the layer just below the crust — is between 50 and 300 ppm (parts per million). This number corresponds to what the research team has identified within the mantle of Mars, based on studies of two chunks of rock — called shergottites — that were blasted off Mars during an impact event 2.5 million years ago.
“We analyzed two meteorites that had very different processing histories,” said Erik Hauri, the analysis team’s lead investigator from the Carnegie Institute . “One had undergone considerable mixing with other elements during its formation, while the other had not. We analyzed the water content of the mineral apatite and found there was little difference between the two even though the chemistry of trace elements was markedly different. The results suggest that water was incorporated during the formation of Mars and that the planet was able to store water in its interior during the planet’s differentiation.”
The water stored within Mars’ mantle may have made its way to the surface through volcanic activity, the researchers suggest, creating environments that were conducive to the development of life.
Like Earth, Mars may have gotten its water from elements available in the neighborhood of the inner Solar System during its development. Although Earth has retained its surface water while that on Mars got lost or frozen, both planets appear to have about the same relative amounts tucked away inside… and this could also be the case for other rocky worlds.
“Not only does this study explain how Mars got its water, it provides a mechanism for hydrogen storage in all the terrestrial planets at the time of their formation,” said former Carnegie postdoctoral scientist Francis McCubbin, who led the study.
Image: The remains of what appears to be a river delta within Eberswalde crater on Mars, imaged by ESA’s Mars Express. Credit: ESA/DLR/FU Berlin (G. Neukum).
A team of NASA-funded researchers led by Carnegie Institution’s Erik Hauri has recently announced the discovery of more water on the Moon, in the form of ancient magma that has been locked up in tiny crystals contained within soil samples collected by Apollo 17 astronauts. The amounts found indicate there may be 100 times more water within lunar magma than previously thought… truly a “watershed” discovery!
Orange-colored lunar soil sampled during Apollo 17 EVA missions was tested using a new ion microprobe instrument which measured the water contained within magma trapped inside lunar crystals, called “melt inclusions”. The inclusions are the result of volcanic eruptions on the Moon that occurred over 3.7 billion years ago.
Because these bits of magma are encased in crystals they were not subject to loss of water or “other volatiles” during the explosive eruption process.
“In contrast to most volcanic deposits, the melt inclusions are encased in crystals that prevent the escape of water and other volatiles during eruption. These samples provide the best window we have to the amount of water in the interior of the Moon.”
– James Van Orman of Case Western Reserve University, team member
While it was previously found that water is contained within lunar magma during a 2008 study led by Alberto Saal of Brown University in Providence, Rhode Island, this new announcement is based upon the work of Brown undergraduate student Thomas Weinreich, who located the melt inclusions. By measuring the water content of the inclusions, the team could then infer the amount of water present in the Moon’s interior.
The results also make correlations to the proposed origins of the Moon. Currently-accepted models say the Moon was created following a collision between the newly-formed Earth and a Mars-sized protoplanet 4.5 billion years ago. Material from the Earth’s outer layers was blasted out into space, forming a ring of molten material that encircled the Earth and eventually coalesced, cooled and became the Moon. This would also mean that the Moon should have similarities in composition to material that would have been found in the outer layers of the Earth at that time.
“The bottom line is that in 2008, we said the primitive water content in the lunar magmas should be similar to lavas coming from the Earth’s depleted upper mantle. Now, we have proven that is indeed the case.”
– Alberto Saal, Brown University, RI
The findings also suggest that the Moon’s water may not just be the result of comet or meteor impacts – as was suggested after the discovery of water ice in polar craters by the LCROSS mission in 2009 – but may also have come from within the Moon itself via ancient lunar eruptions.
The success of this study makes a strong case for finding and returning similar samples of ejected volcanic material from other worlds in our solar system.
“We can conceive of no sample type that would be more important to return to Earth than these volcanic glass samples ejected by explosive volcanism, which have been mapped not only on the Moon but throughout the inner solar system.”
– Erik Hauri, lead author, Carnegie’s Department of Terrestrial Magnetism
The results were published in the May 26 issue of Science Express.
Read the full NASA news release here. | 0.817839 | 4.059397 |
This is an image of Neptune, and shows the Great Dark Spot.
Click on image for full size
A Look at Neptune's Clouds
Like Jupiter and all the giant planets, Neptune's appearance shows a striped pattern of clouds. Other cloud shapes seen over time include a small dark spot, the "scooter
" and the Great Dark Spot. The Great Dark Spot
is the largest of the cloud patterns on Neptune. There are also clouds which are similar to recognizable Earth clouds.
The clouds are found low in the atmosphere of Neptune.
The atmosphere of Neptune is mostly made of a complex molecule called methane.
Hazes of smog on Neptune, made of methane and other, even more complex molecules, are to be found very high up, above the clouds of Neptune.
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Scientists think that the solar system formed out of a spinning cloud of hydrogen and helium molecules. Because the cloud was spinning, it flattened into a frisbee shape, just like a ball of pizza dough...more | 0.811242 | 3.27086 |
August 9, 2017 – An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth’s climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on November 11, 2016, in order to test new technologies that help to measure Earth’s radiation imbalance, which is the difference between the amount of energy from the Sun that reaches Earth and the amount that is reflected and emitted back into space. That difference, estimated to be less than one percent, is responsible for global warming and climate change.
Designed to measure the amount of reflected solar and thermal energy that is emitted into space, RAVAN employs two technologies that have never before been used on an orbiting spacecraft: carbon nanotubes that absorb outbound radiation and a gallium phase change blackbody for calibration.
Among the blackest known materials, carbon nanotubes absorb virtually all energy across the electromagnetic spectrum. Their absorptive property makes them well suited for accurately measuring the amount of energy reflected and emitted from Earth. Gallium is a metal that melts — or changes phase — at around body temperature, making it a consistent reference point. RAVAN’s radiometers measure the amount of energy absorbed by the carbon nanotubes, and the gallium phase change cells monitor the stability of the radiometers.
RAVAN began collecting and sending radiation data on January 25 and has now been in operation for well past its original six-month mission timeframe.
“We’ve been making Earth radiation measurements with the carbon nanotubes and doing calibrations with the gallium phase change cells, so we’ve successfully met our mission objectives,” said Principal Investigator Bill Swartz of Johns Hopkins Applied Physics Laboratory in Laurel, Maryland. He and his team are now monitoring RAVAN in the longer term to see how much the instrument changes over time and are also performing data analysis and comparing its measurements with existing model simulations of outgoing Earth radiation.
While the technology demonstration comprises a single CubeSat, in practice a future RAVAN mission would operate many CubeSats in a constellation. Instruments for measuring Earth’s outgoing energy are currently housed aboard a few large satellites, and while they have a high spatial resolution they cannot observe the entire planet simultaneously the way a constellation of RAVAN CubeSats could, Swartz explained.
“We know that outgoing radiation from Earth varies widely over time depending on variables such as clouds or aerosols or temperature changes,” Swartz said. “A constellation can provide a global, 24/7 coverage that would improve these measurements.”
“This successful technology demonstration realizes the potential of a new observation scenario to get at a very difficult measurement using constellation missions,” said Charles Norton, program area associate for the Earth Science Technology Office (ESTO) at NASA’s Jet Propulsion Laboratory in Pasadena, California. “In terms of its impact for CubeSats and Smallsats for NASA, I think It has helped to bring forward another example of how this platform can be successfully used for technology maturation, validation and science.”
RAVAN is being led by the Johns Hopkins University Applied Physics Laboratory. Blue Canyon Technologies manufactured the spacecraft bus and spearheads the operations out of its advanced Mission Operations Center located in Boulder, Colorado.
RAVAN and other Earth science CubeSat missions are funded and managed by NASA’s Earth Science Technology Office (ESTO) in the Earth Science Division. ESTO supports technologists at NASA centers, industry and academia to develop and refine new methods for observing Earth from space, from information systems to new components and instruments.
Small satellites, including CubeSats, are playing an increasingly larger role in exploration, technology demonstration, scientific research and educational investigations at NASA, including: planetary space exploration; Earth observations; fundamental Earth and space science; and developing precursor science instruments like cutting-edge laser communications, satellite-to-satellite communications and autonomous movement capabilities. | 0.828658 | 3.480764 |
Hubble telescope spies stellar 'land of giants'
Hubble has probed a clutch of monster stars about 170,000 light-years away on the edge of our Milky Way Galaxy.
Some two dozen behemoths were identified, all with masses in excess of a hundred times that of the Sun.
Four were known previously, including the remarkable colossus catalogued as R136a1, which is 250 times as massive as our home star.
But the new survey finds many more of the super-objects in a tight patch of sky within the Large Magellanic Cloud.
"In just a tiny bit of this satellite galaxy, we see perhaps a couple of dozen stars with more than a 100 solar masses, of which nine are in a tight core just a few light-years across," explained Prof Paul Crowther from Sheffield University, UK.
"But that two dozen number - that's probably more than are in the entire Milky Way Galaxy for this type of star," he told BBC News.
The observations are to be published shortly in the Monthly Notices of the Royal Astronomical Society.
They build on earlier work reported in 2010 that first described R136a1 - the most massive and most luminous star identified to date.
That study used data gathered principally by a ground-based telescope in Chile.
This follow-up research employed the pin-sharp resolution and ultraviolet sensitivity of the orbiting Hubble telescope to tease out yet more detail.
In 2010, astronomers saw four monster stars including R136a1 in the central core. Thanks to Hubble, they detect a further five.
The stars are not only extremely massive, but they are also extremely bright. Together, these nine stars outshine our Sun by a factor of 30 million, said Prof Crowther.
"Because they are so massive, they are all close to their so-called Eddington limit, which is the maximum luminosity a star can have before it rips itself apart; and so they've got really powerful outflows. They are shedding mass at a fair rate of knots," the astronomer added - up to an Earth mass of gaseous material per month.
The question is why this tight corner of space, located in the Tarantula Nebula of the LMC, harbours so many giants.
Prof Crowther thinks it is because the gas and dust in the region has become compressed as the Large Magellanic Cloud has skirted the edge of the Milky Way. One thing is for sure - none of these monster stars will be around for more than a few million years. To burn so bright is to burn briefly.
"A lot of these stars will be in binaries (in pairs), and when they die they'll produce black holes, which will merge at some point in the dim and distant future. And when they do they'll produce gravitational waves.
"The first detection of gravitational waves [reported by Advanced LIGO last month] was from the merger of a pair of 30-solar-mass black holes. They probably came from 100-solar-mass stars."
and follow me on Twitter: @BBCAmos | 0.901838 | 3.675095 |
Twin iridescent jets of gas stream outward from a binary planetary nebula at over 1 million kilometers (621,400 miles) an hour.
Space news (September 24, 2015) –
First recorded flying across the constellation Ophiuchus – about 2,100 light-years from Earth – by Rudolph Minkowski in 1947, the Twin Jet Nebula (PN M2-9), or Wings of a Butterfly Nebula, is a remarkably complex and stunningly beautiful 1,200-year-old bipolar planetary nebula.
A bipolar nebula composed of an average star between 1 to 1.4 solar masses nearing the end of its life cycle and a smaller white dwarf between 0.6 to 1.0 solar masses that orbit a common center of mass. The Twin Jet Nebula gets its name from the shape of its two lobes, which look like butterfly wings to many viewers.
Astrophysicists think the shape of the wings (lobes) is mainly due to the unusual motion of the larger star and white dwarf around their common center of mass. Orbiting each other in around 100 years, the smaller white dwarf is thought to have stripped gas away from its larger companion star, which then formed an expanding ring of material around the stars far too small to be seen by Hubble.
This disk of material was then stretched into the shape of two lobes resembling two butterfly wings, rather than a uniform sphere, due to the unusual motion of the two stars around their center of mass. The faint patches of blue within the wings, starting near the binary star system and extending outward horizontally, are twin jets of gas streaming outward at over 1 million kilometers an hour. These jets slowly change their orientation, precessing across the lobes (wings) as the two stars orbit each other.
Astrophysicists are now taking a closer look at the Twin Jet Nebula, and other bipolar nebulae, to try to determine if such systems always contain two stars orbiting a common center of mass. Currently, astronomers are discussing this possibility, and other scenarios possibly leading to the birth and growth of similar celestial objects and other phenomena.
Two astronomers working with NASA’s Hubble Space Telescope and the ESO’s New Technology Telescope also recently conducted a study of 130 planetary nebulae. Dr. Brian Rees and Dr. Albert Zijlstra of the University of Manchester in the United Kingdom found the long axis of many bipolar planetary nebulae studied all line up along the plane of the Milky Way. This alignment could have something to do with the magnetic field of the bulge at the center of our galaxy they think. You can read the abstract here.
You can learn more about bipolar nebulae here.
Go here to learn about NASA’s mandate to travel to the planets and beyond.
Discover the Hubble Space Telescope here.
Learn more about main sequence suns like our Sol. | 0.915944 | 3.842812 |
Galaxy NGC 6052 is being formed into a single structure from the merging of two galaxies of similar mass
Space news ( February 18, 2016) – 230 million light-years away in the constellation Hercules –
This breathtaking Hubble image of galaxy NGC 6052 was taken with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. Astronomers originally classified this different looking island universe as an irregular galaxy, but after more study, they believe it’s a new galaxy in the process of being formed.
Also called Mrk 297, LEDA 57039 and Arp 209, NGC 6052 has previously been described as having a rather unusual structure, as seen in the regions of strong emission and the irregular appendage on its eastern side as seen in this image.
Looking at the image, it’s not easy to see the traces of two separate galaxies in the act of merging. Attracted by gravity, two smaller galaxies with similar mass were slowly drawn together, before colliding to form NGC 6052.
As the merging process progresses, individual stars are knocked out of their original orbits and onto new ones that take them far outside the galaxy. The starlight in the image appears quite chaotic in shape and form, but over time, the chaotic shape of this new galaxy will settle down.
Astronomers conducting a survey of nearby galaxies detected all types on the Hubble Tuning Fork, with about ten percent on average being classified as irregular or unusual using the Hubble classification system. The sample size in this survey is rather small, though, when you compare it to the size of the cosmos.
The percentages of different galaxy types seem to vary according to the environment, so astronomers expect these numbers to change as the survey sample size increases.
A titanic collision
Billions of years in the future, Andromeda and the Milky Way will have a similarly fated meeting, but this galactic merger will be a cosmic collision of a different sort. Andromeda has much more mass and is bigger than the Milky Way and astronomers expect this meeting to produce a different looking island universe than NGC 6052.
Learn more about NASA past and future here.
Take the journey of the Hubble Space Telescope.
Learn more about the Hubble classification system.
Learn more about NGC 6052.
Discover galaxy types and the Hubble Tuning Fork here.
Learn more about the evolution and formation of the Milky Way. | 0.859493 | 3.510571 |
The Moon dances, spins and twirls and crater Goddard arcs past your view
The Moon was one of the first celestial objects viewed by man
Star gazers can pay respects to a true pioneer of human space travel Robert Goddard beginning on the night of October 10th, by taking a journey to the Moon to view the crater named after this gentleman of astronomy. Your view of the Moon’s crescent will show plenty of open landscape between the Moon’s eastern limb and Mare Crisium on this night.
Astronomy News – A large oval plain encompassing an area 270 miles wide by 350 miles long, with the long side running east to west, Mare Crisium will appear different on this night because of the foreshortening of the lunar globe. Mare Crisium also stands alone on the surface of the Moon and isn’t interconnected with the other maria you’ll view on the Moon’s surface during your “Journey to the Beginning of Space and Time”. The last place on the Moon’s surface to be visited by mankind, Mare Crisium, or the Sea of Crises, was host to the unmanned soviet spacecraft Luna 24 in 1976. Look for dark patches along the Moon’s limb on October 10th, which is actually hardened lava of Mare Marginis, the Sea on the Margin, and finds the short white arc just beyond the eastern shore of the sea. This short white arc is the illuminated rim of crater Goddard. Watch as Goddard arcs past the Moon’s eastern limb over the next few nights and you’ll get a good lesson in how the Earth’s satellite moves as the Moon’s eastern limb rotates away from Earth.
On October 15th, Goddard will appear in profile and you should see the rim of this crater poking outward, like two towering peaks framing a darker interior. On October 18th, Goddard will have disappeared over the limb and only about half of Mare Marginis will be viewable. On October 22nd, the Moon will be in full phase at 9:37 P.M. EDT and only an outline of the shoreline of Mare Marginis will be visible. By this time, Mare Crisium will appear much closer to the limb and is prominent in your view of the Moon.
Take a young astronomer on a journey to the Moon tonight
Why does Mare Crisium appear closer and what causes this visual sleight-of-hand? The Moon actually spins at a pretty constant rate, generally completing one rotation on its axis each month. In the same time frame, however, the Moon orbits the Earth on an elliptical path, and this means the Moon’s speed of rotation will vary. This allows viewers to see a few degrees beyond the normal limb of the Moon during specific time frames of the lunar cycle, which is an effect an astronomer refers to as the libration of the Moon. | 0.855657 | 3.293957 |
Powerful beams of radiation continually shooting across 300,000 light-years of spacetime
This new composite image of the beam of particles was obtained by combining X-ray data (blue) from NASA’s Chandra X-ray Observatory at various times over a fifteen year period and radio data from the Australian Telescope Compact Array (Red). Astronomers gain understanding and knowledge of the true nature of these amazing jets by studying and analyzing details of the structure of X-ray and radio data obtained.
Image credit: NASA/JPL/Chandra
Space news (February 25, 2016) – 500 million light-years away in the constellation Pictor –
The stunning Chandra X-ray image of radio galaxy Pictor A seen here shows an amazing jet that reminds one of the death rays from Star Wars emanating from a black hole in the center of the galaxy. The “Death Star” as portrayed in the Star Wars movie Star Wars: Episode IV A New Hope was capable of totally destroying a planet using powerful beams of radiation. In just the same any planet finding itself in the direct path of the 300,000 light-years long, continuous jet emanating from the supermassive black hole in the center of a galaxy is toast.
Astronomers think the stunning jet observed is produced by huge amounts of gravitational energy released as material swirls toward the point–of–no–return in the gravity well of the supermassive black hole at its center the event horizon. These jets are an enormous beam of particles traveling at nearly the speed of light into the vastness of intergalactic space scientists call relativistic jets.
Astronomers also report additional data confirming the existence of another jet pointing in the opposite direction to the jet seen in this image that they call a counter jet. Data had previously pointed to the existence of a counter jet and the latest Chandra data obtained confirmed this. Unfortunately, due to the motion of this opposite jet away from the line-of-sight to Earth, it’s very faint and hard for even Chandra to observe.
Current theories and computer simulations indicate the continuous X-ray emissions observed by Chandra could be produced by electrons spiraling around magnetic field lines in a process astronomers call synchrotron emission. They’re still trying to figure out how electrons could be continuously accelerated as they travel the length of the jet. But plan additional observations in the future to obtain more data to help develop new theories and computer simulations to explain this.
We’ll update you on any new developments and theories on jets emanating from supermassive black holes at the center of nearby galaxies as they’re developed.
You can learn more about jets emanating from supermassive black holes here.
Follow the journey of the Chandra X-ray Observatory here.
Learn more about relativistic jets here.
Read about astronomers recent discovery that superstar binaries like Eta Carinae are more common than first thought.
Read and observe the hydrocarbon dunes of Saturn’s moon Titan. | 0.865691 | 3.725957 |
Extrasolar planets, or exoplanets, are planets that orbit stars other than our sun. Astronomers like Dr. William Welsh at San Diego State University primarily use two methods to detect these distant planets: Doppler and Transit methods. "Science Behind the News" is produced in partnership with the National Science Foundation.
Science Behind the News -- Extrasolar Planets
ANNE THOMPSON reporting:
For centuries, humans have looked to the night sky and wondered if there were any other planets out there like Earth, orbiting the distant stars. Then, in 1992, astronomers made the first discovery of a planet orbiting an alien star. Since that time, more than 700 extrasolar planets, or exoplanets, have been identified.
Dr. WILLIAM WELSH (San Diego State University): An extrasolar planet is a planet that orbits a star that's not our Sun.
THOMPSON: Dr. William Welsh is an astronomer at San Diego State University and funded by the National Science Foundation. He and other astronomers have been able to measure the size and mass of hundreds of these exoplanets, though some thousands of light years away, meaning that even if we could travel at the speed of light, it would still take us thousands of years to get there.
WELSH: So those little dots of light in the sky might have planets around them. An extrasolar planet would be a planet that orbits one of those little dots of light.
THOMPSON: To detect these distant planets, astronomers primarily use two methods: Doppler and Transit. The Doppler Method measures a star's “wobble”, something caused by the force of gravity from exoplanets themselves pulling, their stars in different directions during their orbit.
DR. WILLIAM WELSH (San Diego State University): They're moving back and forth in the sky and we're able to detect that motion through a technique called spectroscopy, which uses the Doppler technique to measure the speed of the star.
THOMPSON: The Doppler Effect is often associated with the change in the frequency of sound waves caused by a moving object, such as the sound of a race car whizzing by. Astronomers use the same principle to analyze how the movement of the star away and towards us, due to its orbiting exoplanet, changes the frequency of light waves. By using spectroscopy, it is possible to measure the frequency shifts in the star's light spectrum, implying movement of the star.
WELSH: It's making a little orbit in the sky by measuring that orbit, we can tell that there's another object there, and that other object is often a planet.
THOMPSON: Measuring the star's wobble also allows astronomers to calculate the planet's mass. The greater the wobble of the star, the greater the mass of the exoplanet. The second method used to identify exoplanets is the Transit Method. After observing a star over a period of time, astronomers sometimes notice a faint dimming of its light. This dimming is likely caused by a planet orbiting past it.
WELSH: The idea is the planet goes in front of the star and makes a little eclipse. And that little eclipse allows us to measure the change in brightness of the star. If that eclipse occurs over and over, then we know that something's orbiting the star and we can determine that there's a planet there. Now, the great thing about transits is that it gives us the size of the planet.
THOMPSON: As Welsh describes it, spotting one of these eclipses is a bit like trying to see an insect crawl across the headlight of a car miles away.
WELSH: Now, imagine a very small ant crawls across the front of that headlight, that's the amount of dimming that you would get when the earth passes in front of the Sun if we were to look at the Sun from very far away.
THOMPSON: Using Doppler and Transit Methods, astronomers are able to determine other characteristics of an exoplanet.
WELSH: The Doppler technique gives us the mass, the transit technique gives us the radius or the actual physical size of the planet. By combining those two different measurements we can get the density of the planet and find out is it a rocky planet like earth or is it a gaseous giant planet like Jupiter.
THOMPSON: Welsh's goal is not to find Jupiter-like planets, but ones more like Earth, a rocky planet with water, making it more likely that it could sustain life. One characteristic of such an Earth-like exoplanet is that it must orbit in what astronomers call the "habitable zone" of its parent star.
WELSH: The habitable zone is sometimes known as the Goldilocks Zone, where it's just the right temperature. It's not too hot and not too cold. But it's just the right temperature where we can have water. And water is what we think is required for life.
THOMPSON: To accomplish this goal, Welsh and fellow planet-hunters will continue to scour the night sky looking for exoplanets and perhaps answer an age-old question: does another Earth exist?
One of our closest celestial neighbors is a warm, rocky world, scientists say.
Writing in the journal Astronomy and Astrophysics, scientists report the discovery of an Earth-size exoplanet orbiting the star Ross 128, a dim red dwarf just 11 light-years away.
Planets, Extrasolar, Exoplanets, Telescopes, Astronomy, Astronomers, William Welsh, San Diego State University, Solar System, Stars, Space, Galaxy, Orbit, Alien, Identification, Sun, National Science Foundation, NSF, Size, Mass, Measurements, Light Years, Light, Detection, Observation, Doppler, Wobble, Method, Shift, Effect, Transit, Motion, Spectroscopy, Spectrum, Sound Waves, Light Waves, Movement, Frequency, Gravity, Eclipse, Radius, Characteristics, Density, Earth, Jupiter, Rocky, Gaseous, Liquid, Water, Life, Habitable Zone, Goldilocks Zone, Temperature | 0.913426 | 3.805696 |
IRAS - the Infrared (heat radiation) Astronomy Satellite - has greatly expanded astronomers' knowledge of the universe. Recently reported findings of its now completed 10-month mission, have shown:
* Something like 10 percent (more than 40) of several hundred nearby stars may be surrounded by orbiting debris such as that from which our own solar system planets once formed.
* ''An unexpectedly high percentage'' - some 25 percent - of galaxies may be colliding or interacting with each other.
* Comets are much dustier than had been realized. Long comet tails of ice and dust, unseen by visible light, show up in the infrared.
* Away from the plane of our own Milky Way galaxy, the sky seen at infrared wavelengths is dominated by spiral galaxies. Some of these emit 50 to 90 percent of their radiant energy in the infrared - ''an exciting and surprising result,'' according to IRAS scientists.
Such are the first fruits from a survey of nearly 98 percent of the sky that had been impossible before IRAS was orbited as a joint British, Dutch, and US project on Jan. 25, 1983.
Reported in the April 6 issue of the journal Science and presented this week to a meeting of the American Astronomical Society (AAS) in Baltimore, they give point to the cliche that astronomers didn't realize how much they had been missing. Now they have a heaping plateful of discoveries to follow up with further research.
This is typical of what happens when astronomers can view the cosmos at wavelengths that had previously been denied them. The advent of radio telescopes and X-ray observing satellites have given new perspectives on the universe. Now astronomers are able to study celestial objects and dust and gas by the heat radiation they emit - something nearly impossible without a satellite.
To quote from the report in Science by 12 IRAS scientists: ''Without IRAS, atmospheric absorption and the thermal emission from both the atmosphere and Earthbound telescopes (themselves) make the task of the infrared astronomer comparable to what an optical astronomer would face if required to work only on cloudy afternoons.''
This ability to ''see'' heat radiation has enabled IRAS sensors to detect dark material orbiting other stars. The stars Vega (fifth brightest in the sky) and Fomalhaut were found to be ringed by what appears to be small orbiting solid bodies. Now, Harmut H. Aumann of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif. - one of the authors of the Science paper - told the AAS meeting such material may be orbiting more than 40 nearby stars. This is a sample of 335 stars within 75 light years of Earth. Perhaps 10 percent of nearby stars have such orbiting debris. This suggests, but does not yet prove, that the conditions for planet formation are widespread in our galaxy.
Another author of the Science paper, Carol J. Lonsdale of JPL, told the AAS meeting that recent studies of IRAS observations of about 20,000 galaxies shows that some 25 percent of galaxies with high infrared emission may be interacting with other galaxies. That's ''an unexpectedly high percentage,'' according to information released by JPL. Dr. Lonsdale explained that the shock of galaxy collision may trigger great bursts of star formation. This would heat interstellar dust and gas which would radiate strongly in the infrared. One such colliding galaxy pair - known by its catalog number Arp 220 - emits 100 times the power of a normal spiral galaxy, with 99 percent of this being radiated in the infrared.
B. Thomas Soifer of JPL and also an author of the Science report, pointed out that Arp 220 has the same characteristics as do some ''unidentified'' objects IRAS has discovered. He told the AAS meeting this suggests that such objects may also be galaxies. They would be more distant and even more luminous than Arp 220 .
Thus IRAS has given astronomers a very challenging new look at the universe. | 0.879069 | 3.951003 |
Migration of stars
Oscillations from the Milky Way disk seem to relocate stars to large vertical distances from their place of birth
Astronomers, led by Maria Bergemann from the Max Planck Institute for Astronomy in Heidelberg, have investigated a small population of stars in the halo of the Milky Way Galaxy, finding its chemical composition to closely match that of the Galactic disk. This similarity provides compelling evidence that these stars have originated from within the disc, rather than from merged dwarf galaxies. The reason for this stellar migration is thought to be theoretically proposed oscillations of the Milky Way disk as a whole, induced by the tidal interaction of the Milky Way with a passing massive satellite galaxy.
If anyone from outer space would like to contact you via “space mail”, your cosmic address would include several more lines including “Earth”, “Solar System”, “Orion Spiral Arm” and “Milky Way Galaxy”. This position within our home galaxy gives us a front row seat to explore what is happening in such a galaxy.
However, our internal perspective presents some challenges in our quest to understand it - for example for outlining its shape and extent. And yet another problem is time: How can we interpret galactic evolution if our own life span (and that of our telescopes) is far less than the blink of the cosmic eye?
Today, we have a fairly clear picture of the broad properties of the Milky Way and how it fits among other galaxies in the Universe. Astronomers classify it as a rather average, large spiral galaxy with the majority of its stars circling its center within a disk, and a dusting of stars beyond that orbiting in the Galactic halo.
These halo stars seem not to be randomly distributed around the halo - instead many are grouped together in giant structures - immense streams and clouds of stars, some entirely encircling the Milky Way. These structures have been interpreted as signatures of the Milky Way’s tumultuous past - debris from the gravitational disruption of the many smaller galaxies that are thought to have invaded our Galaxy in the past.
Researchers have tried to learn more about this violent history of the Milky Way by looking at properties of the stars in the debris left behind - their positions and motions can give us clues of the original path of the invader, while the types of stars they contain and the chemical compositions of those stars can tell us something about what the long-dead galaxy might have looked like.
An international team of astronomers lead by Dr. Maria Bergemann from the Max Planck Institute for Astronomy in Heidelberg now found compelling evidence that some of these halo structures might not be leftover debris from invading galaxies but rather originate from the Milky Way’s disc itself!
The scientists investigated 14 stars located in two different structures in the Galactic halo, the Triangulum-Andromeda (Tri-And) and the A13 stellar overdensities, which lie at opposite sides of the Galactic disc plane. Earlier studies of motion of these two diffuse structures revealed that they are kinematically associated and could be related to the Monoceros Ring, a ring-like structure that twists around the Galaxy. However, the nature and origin of these two stellar structures was still not conclusively clarified. The position of the two stellar overdensities could be determined as each lying about 5 kiloparsec (14000 lightyears) above and below the Galactic plane (figure).
Bergemann and her team, for the first time, now presented detailed chemical abundance patterns of these stars, obtained with high-resolution spectra taken with the Keck and VLT (Very Large Telescope, ESO) telescopes. “The analysis of chemical abundances is a very powerful test, which allows, in a way similar to the DNA matching, to identify the parent population of the star. Different parent populations, such as the Milky Way disc or halo, dwarf satellite galaxies or globular clusters, are known to have radically different chemical compositions. So once we know what the stars are made of, we can immediately link them to their parent populations.”, explains Bergemann.
When comparing the chemical compositions of these stars with the ones found in other cosmic structures, the scientists were surprised to find that the chemical compositions are almost identical, both within and between these groups, and closely match the abundance patterns of the Milky Way disc stars. This provides compelling evidence that these stars most likely originate from the Galactic thin disc (the younger part of Milky Way, concentrated towards the Galactic plane) itself, rather being debris from invasive galaxies!
But how did the stars get to these extreme positions above and below the Galactic disk? Theoretical calculations of the evolution of the Milky Way Galaxy predict this to happen, with stars being relocated to large vertical distances from their place of birth in the disc plane. This “migration” of stars is theoretically explained by the oscillations of the disc as a whole. The favoured explanation for these oscillations (or waves) is the tidal interaction of the Milky Way’s Dark matter halo and its disk with a passing massive satellite galaxy.
The results published in the journal Nature by Bergemann and her colleagues now provide the clearest evidence for these oscillations of the Milky Way’s Dark disc obtained so far!
These findings are very exciting, as they indicate that the Milky Way Galaxy's disk and its dynamics are significantly more complex than previously thought. “We showed that it may be fairly common for groups of stars in the disk to be relocated to more distant realms within the Milky Way—having been 'kicked out' by an invading satellite galaxy. Similar chemical patterns may also be found in other galaxies—indicating a potential galactic universality of this dynamic process.” said Allyson Shefield from LaGuardia Community College/CUNY, a co-author on the study.
As a next step, the astronomers plan to analyse the spectra of other stars both in the two overdensities, as well as stars in other stellar structures further away from the disc. They are also very keen on getting masses and ages of these stars in order to constrain the time limits when this interaction of the Milky Way and a dwarf galaxy happened.
“We anticipate that ongoing and future surveys like 4MOST and Gaia will provide unique information about chemical composition and kinematics of stars in these overdensities. The two structures we have analysed already are, in our interpretation, associated with large-scale oscillations in the disc, induced by an interaction of the Milky Way and a dwarf galaxy. Gaia may have the potential to see the connection between the two structures, showing the full oscillation pattern in the Galactic disc”, says Bergemann, who is also part of the Collaborative Research Center SFB 881 “The Milky Way System”, located at Heidelberg University.
RH / HOR | 0.857643 | 4.020237 |
When corrected for the effects of propagation in the interstellar medium (i.s.m.), the observed composition of galactic cosmic rays can give us some clues as to the origin of these particles. It is noteworthy that the main pecularities of the cosmic ray source composition (CRS), as compared to normal i.s.m. abundances, bear some resemblance to that of i.s. grains, as inferred from i.s. absorption line measurements (e.g. York 1976): (1) the refractory elements Al, Si, Mg, Ni, Fe and Ca, which in i.s. clouds are almost completely locked into grains, are present with normal abundance ratios in the CRS. (2) normalized to Si, the volatile and reactive elements C, N, O, S and Zn are underabundant in CRS by factors of 2.5 to 6; these elements are only partially depleted in the i.s.m. (3) at a given rigidity the ratios H/Si and He/Si are lower than in the i.s.m. by a factor of ~ 25; while H and He atoms are virtually absent in i.s. grains. (1) implies that cosmic rays originate in astrophysical sites where the grains have either not condensated as yet, or where they have been (at least partially) destroyed. Then, to account for (2) and (3), one might consider that an unspecified mechanism selects the particles to be accelerated, possibly according to their first ionization potential (Cassé 1979 and references there-in). | 0.801711 | 3.881677 |
On Sunday at eleven:03 p.m. EST, the European Place Company and NASA efficiently launched their joint Photo voltaic Orbiter mission from Cape Canaveral Air Drive Station in Florida, with the spacecraft catching a journey aboard a United Launch Alliance Atlas V rocket.
Through its mission, the Photo voltaic Orbiter will get up shut and particular with the solar in get to investigate our host star and its magnetic subject, as properly as how the solar influences our photo voltaic technique as a full. Nevertheless the spacecraft will shell out a handful of a long time easing into its exceptional elliptical orbit all around the solar, at the time there, it will be properly positioned to also study the sun’s poles up shut for the 1st time.
Geared up with a camera, the orbiter’s particular orbit — which often will take it closer to the solar than Mercury at any time gets — will permit the spacecraft to snap the 1st-at any time pictures of the sun’s poles. In excess of the course of its mission, scientists program to have the Photo voltaic Orbiter make 22 shut approaches to the solar.
For the 1st two days pursuing its launch, the orbiter will initiate communications with Earth and start collecting information. The future 3 months of the mission will be applied to make sure its instruments are functioning correctly. Then, the Photo voltaic Orbiter will shell out two a long time (dubbed the “cruise phase”) reaching its sought after orbit. In the meantime, it’ll nonetheless be accumulating information before it begins its primary aim.
There are ten distinctive instruments onboard the orbiter that will collaboratively study the solar, such as a noticeable gentle telescope and tools to seize photo voltaic wind particles, dust and cosmic rays.
The Parker Photo voltaic Probe, which launched in 2018, will function in conjunction with the Photo voltaic Orbiter. When the Parker probe is smaller sized, it can be equipped to go closer to the solar, but it doesn’t have cameras to seize what it sees. The Photo voltaic Orbiter does. Concerning the two, scientists will lastly be equipped to have a improved comprehension of the star that lets life on Earth hold chugging along.
“As humans, we have often been common with the importance of the Sunlight to life on Earth, observing it and investigating how it operates in detail, but we have also long regarded it has the potential to disrupt day-to-day life ought to we be in the firing line of a powerful photo voltaic storm,” Günther Hasinger, ESA director of science, claimed in a NASA press release. “By the conclusion of our Photo voltaic Orbiter mission, we will know additional about the hidden pressure liable for the sun’s modifying behavior and its affect on our house world than at any time before.” | 0.857277 | 3.443663 |
On October 3, 2011, first images produced by the Atacama Large Millimeter Array were released to the press. The Atacama Large Millimeter/submillimeter Array (ALMA) is an astronomical interferometer of radio telescopes in the Atacama desert of northern Chile. ALMA is currently the largest and most expensive ground-based astronomical project, costing between US$1.4 and 1.5 billion.
ALMA is an interferometer, i.e. ,amy small radio telescopes working together as a single large telescope. The telescope dishes can be picked up and rearranged by special large transport vehicles. The water vapor in the Earth’s atmosphere absorbs radio waves, making radio astronomy difficult from sea level. Thus, for ALMA a plateau has been chosen about 5,000 meters above sea level in the Chilean Atacama desert, placing it above 40 percent of the Earth’s atmosphere. Each individual dish is up to 12 metres in diameter and weighs 115 tons. The ALMA radio telescope receives wavelengths of around 1 millimeter, between the infrared and radio parts of the electromagnetic spectrum.
ALMA has its conceptual roots in the Millimeter Array (MMA) project of the United States, the Large Southern Array (LSA) project of Europe, and the Large Millimeter Array (LMA) project of Japan. In 1997, when the NRAO (National Radio Astronomy Observatory) and the ESO (European Southern Observatory) agreed to pursue a common project that merged the MMA and LSA, combining the sensitivity of the LSA with the frequency coverage and superior site of the MMA. The name “Atacama Large Millimeter Array”, or ALMA, was chosen for the new array in March 1999 and the signing of the ALMA Agreement on 25 February 2003, between the North American and European parties. A proposal from the NAOJ (National Astronomical Observatory of Japan) suggested that Japan would provide the ACA (Atacama Compact Array) and three additional receiver bands for the large array, to form Enhanced ALMA, to be known as the Atacama Large Millimeter/submillimeter Array. A groundbreaking ceremony was held on November 6, 2003.
For political reasons it was decided to employ ALMA antennas designed and constructed by known companies in North America, Europe, and Japan, rather than using one single design. The initial ALMA array is composed of 66 high-precision antennas, and operate at wavelengths of 0.3 to 9.6 mm. The array has much higher sensitivity and higher resolution than earlier submillimeter telescopes or existing interferometer networks. The array has been constructed on the Chajnantor plateau in the Atacama desert of northern Chile at 5,000 metres altitude, near Llano de Chajnantor Observatory and Atacama Pathfinder Experiment. The antennas can be moved across the desert plateau over distances from 150 m to 16 km, which will give ALMA a powerful variable “zoom”, similar in its concept to that employed at the Very Large Array (VLA) site in New Mexico, United States.
In 2011, sufficient telescopes were operational during the extensive program of testing prior to the Early Science phase for the first images to be captured. The target of the observation was a pair of colliding galaxies with dramatically distorted shapes, known as the Antennae Galaxies. Although ALMA did not observe the entire galaxy merger, the result is the best submillimeter-wavelength image ever made of the Antennae Galaxies, showing the clouds of dense cold gas from which new stars form, which cannot be seen using visible light.
In 2014, an image of the protoplanetary disk surrounding HL Tauri (a very young T Tauri star in the constellation Taurus approximately 450 light-years from Earth) was made public, showing a series of concentric bright rings separated by gaps, indicating protoplanet formation. The disk appeared much more evolved than would have been expected from the age of the system, which suggests that the planetary formation process may be faster than previously thought. One theory suggests that the faster accretion rate might be due to the complex magnetic field of the protoplanetary disk
At yovisto you can learn more about the history of ALMA from the origins of the project several decades ago to the recent first science results.
References and Further Reading: | 0.817339 | 3.56536 |
A new image taken by an array of radio telescopes is the best resolution view ever of particle jets erupting from a supermassive black hole in a nearby galaxy. An international team of astronomers targeted Centaurus A (Cen A), and the image shows a region less than 4.2 light-years across — less than the distance between our sun and the nearest star. Radio-emitting features as small as 15 light-days can be seen, making this the most detailed image yet of black hole jets.
“These jets arise as infalling matter approaches the black hole, but we don’t yet know the details of how they form and maintain themselves,” said Cornelia Mueller, the study’s lead author and a doctoral student at the University of Erlangen-Nuremberg in Germany.
The data was gathered by the TANAMI project (Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry), an intercontinental array of nine radio telescopes.
While not completely understood, black hole particle jets typically escape the confines of their host galaxies and flow for hundreds of thousands of light years. They are somewhat a paradox, because while black holes are known for pulling matter in, they also produce these jets which accelerate matter at near light speed.
They are a primary means of redistributing matter and energy in the universe, and understanding them will be key to understanding galaxy formation and other cosmic mysteries such as the origin of ultrahigh-energy cosmic rays.
While the black hole is invisible, the jets are seen in great detail in the new image. Cen A is located about 12 million light-years away in the constellation Centaurus and is one of the first celestial radio sources identified with a galaxy.
Seen in radio waves, Cen A is one of the biggest and brightest objects in the sky, nearly 20 times the apparent size of a full moon. This is because the visible galaxy lies nestled between a pair of giant radio-emitting lobes, each nearly a million light-years long.
These lobes are filled with matter streaming from particle jets near the galaxy’s central black hole. Astronomers estimate that matter near the base of these jets races outward at about one-third the speed of light.
The new study will appear in the June issue of Astronomy and Astrophysics and is available online. | 0.860269 | 3.930908 |
Aphelion & Perihelion8.5 -Understand the terms ‘aphelion’ and ‘perihelion’ (solar orbits), ‘apogee’ and ‘perigee’ (Earth orbits) for an elliptical orbit
Planets and comets do not orbit in perfect circles. They orbit in ellipses.
The point at which they are nearest the Sun (or focus, such as a moon around a planet) is called perihelion.
The point at which they are furthest from the Sun is called aphelion.
An orbit is the path of a body (such as a planet, moon or comet etc.) around another. The Earth travels around the Sun in 365.25 days.
The orbit of the Earth is not quite circular. The shape of the Earth's orbit is an ellipse. It is an elliptical orbit.
This is like an oval orbit. Most objects in the Solar System follow an elliptical orbit.
One part of an ellipse is nearer to the Sun than the other.
PERIHELION = Body NEARER to Sun
APHELION = Body FURTHER from Sun
When the Earth is nearest to the Sun (in January) it is in PERIHELION or perigee and is 147,000,000 km from it.
When it is furthest from the Sun (in July) it is in APHELION or apogee. It is then 153,000,000 km from the Sun.
The mean average distance is approximately 150,000,000 km. This is called the Astronomical Unit, or AU.
We use the terms Perigee and Apogee to describe one objects relationship to another. So at one point of the Moon's elliptical orbit around Earth it will be in perigee at its closest and apogee at its furthest point from Earth.
PERIGEE = Body NEARER to orbiting body
APOGEE = Body FURTHER from orbiting body | 0.804192 | 3.637472 |
BEYOND EINSTEIN PDF
The Beyond Einstein program aims to answer these questions. Beyond Einstein fascinates the American public and compels the attention of the news. are beyond the scope of this thesis, and we refer the reader to the reviews . theory of gravity we will be modifying: Einstein's general relativity. The Philosophy of Psychology What is the relationship between common-sense, or 'folk', psychology and contemporary s.
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myavr.info 1. Beyond Einstein: non-local physics Einstein's Special and General Relativity theories, have proven to be very useful in the several. PDF | This article provides a review of the latest experimental results in quantum physics and astrophysics, discussing their repercussions on the advanced. Beyond Einstein takes readers on an exciting excursion into the discoveries that have led scientists to the brightest new prospect in theoretical.
Cadenza LISA will open a new window on the Universe through the study of low-frequency gravitational waves. The laser light received from the two distant spacecraft is combined with the light from the local lasers. LISA will have greatest sensitivity to gravitational waves of periods of to seconds.
Combining the signals from all the pairs of spacecraft will permit detection of both of the two polarizations of gravitational waves of the waves. At the heart of each spacecraft are two free-flying reference masses for the detection of gravitational waves.
The Constellation-X mission has been in formulation since with a focused technology development program. Recent technology investments provide a clear path for future efforts that would support launches as early as These two elements. Sources will be distinguished by studying the time evolution of their waveforms. Micronewton thrusters will maintain drag-free control of the spacecraft about the proof masses.
In one year of observation. Two cm telescopes direct the beams from two cavity-stabilized lasers toward the other two spacecraft. LISA will simultaneously observe a wide variety of sources from all directions in the sky. The major science objectives of LISA include: No other signal survives from that era. LISA will be the first instrument capable of detecting gravitational waves from already cataloged objects several binary stars. None of these can be detected by ground-based detectors.
Their orbital trajectories determine the full spacetime geometry down to the event horizon. Sources of gravitational waves that LISA should detect include all the thousands of compact binaries in our own Galaxy. LISA may also detect violent events in the early Universe. The desire for precise measurements of these weak signals set the sensitivity goals for LISA. LISA measures periods between 10 seconds and a few hours.
This will allow detailed observations of information-rich. This will probe energy and length scales characteristic of the Universe seconds after the Big Bang. Although they run on general principles similar to LISA. LIGO and other ground-based laser-interferometer gravitational wave observatories are beginning operation.
LISA will also detect or strongly constrain the rate of mergers of intermediate mass or seed black holes. LISA will be able to observe for a year or more any merger of supermassive black holes in merging galaxies. For example. LIGO will hear the final few minutes of radiation from merging black hole remnants of ordinary binary stars about ten or more times the mass of the Sun. There are several plausible strategies.
Probing dark energy requires measuring precisely how the expansion rate of the Universe is. Einstein Probes Dark Energy Probe The nature of the mysterious dark energy that dominates our Universe is one of the newest and most important questions facing cosmology and fundamental physics today. With technological advances. Because they are on the ground. As a result they are optimized to detect waves of much shorter periods than LISA.
The Department of Energy has begun such development and is an interested partner in such a mission. The sensitivity would be required to allow source detection down to 29th magnitude at 1 micron. Considerable technology investment would be necessary to develop reliable detector arrays of such large format. If the Dark Energy Probe shows that the dark energy density varies with time.
We now know that his constant is equivalent to an energy density of the vacuum. We can use our current understanding of how quantum mechanics and gravity join to estimate what the energy density of that vacuum should be. Pinning down the precise value will both verify the existence of this mysterious component beyond any doubt and.
More dramatic alternative candidates for dark energy include dynamically evolving fields or even a breakdown of the general theory of relativity. A mission of this type could search for large numbers of Type Ia supernovae in the redshift range 0.
To decide which is right. An experimental measurement of a small but nonzero cosmological constant would dramatically influence the search for a quantum theory of gravity. HgCdTe collectively providing multicolor coverage over the range 0. The result is times larger than the experimental limits! Our understanding is clearly incomplete. This could be accomplished by repeatedly scanning a limited region of sky about 10 square degrees.
The focal plane would consist of billion-pixel arrays of CCDs and near-infrared detectors e. If the Dark Energy Probe shows that the dark energy density is constant in time.
Many of the Beyond Einstein missions require that they be located far from Earth. This will provide the most precise test yet of the gravitational theory for the origin of galaxies and structure in our Universe.
Both density fluctuations and gravitons gravitational wave quanta produced in the very early Universe combined to determine this pattern. One promising approach would use a 2-meter cooled telescope located at L2. Just before the Universe became neutral. This generated a pattern of polarization related to the temperature fluctuations of the CMB. Constellation-X and the Inflation Probe require thermal control and will orbit around L2.
Temperature anisotropy studies. The Inflation Probe will: The L2 point is located approximately 1. It will also test physics at energies that are currently inaccessible by any other means.
Each pixel must also be observed simultaneously from 50— GHz to allow astrophysical foregrounds to be subtracted.
Did massive black holes form when galaxies formed? Did they slowly grow later? How fast are they still growing? We need a census of accreting black holes to find out. The detectors that will fly on Planck are already close to fundamental quantum limits.
This will test theories of the very early Universe. The signals from inflation are likely to be mixed with confusing foregrounds and effects from gravitational lensing. The optical appearance of a galaxy usually does not advertise the presence of a black hole. Even the three closest supermassive black holes now swallowing gas are hidden in galaxies that otherwise appear normal.
The angular resolution of the maps must be a few arcminutes to allow the true gravitational wave signal to be distinguished from secondary sources of polarized CMB signals. Yet these black holes have had a dramatic effect on the formation and evolution of galaxies— and even life. This simulation shows the circular patterns gravitational waves as long as the Universe leave in the polarization of the cosmic microwave background.
The Black Hole Finder Probe will enable a range of studies of black holes and the extremes of astrophysics: The required angular resolution is about 3— 5 arcmin. It can identify the most luminous obscured black holes at larger redshifts to estimate the growth rate of massive black holes.
To perform a reliable census. X-rays can best be distinguished from emission from stars. A veil of dust and gas currently hides most accreting black holes from our view. It will perform the first all-sky imaging census of accreting black holes: It will complement LISA.
Highenergy X-rays. Follow-up studies with Constellation-X and eventually the Black Hole Imager will measure fundamental black hole properties spin. Besides the familiar stars. The faintest survey sources would have 1 arcmin centroids. Of these. To penetrate gas and dust. Like electromagnetic waves. This could give us a direct view of the creation of space and time and.
In between. They will also enable even finer measurements of the structure of spacetime around black holes than will be possible with LISA. To reduce the risks.
The ultimate goal of the Big Bang Observer is the direct detection of these gravitational waves. At the shorter periods at which ground-based gravitational wave detectors must operate. The hydrogen and helium around us formed when the Universe was a few minutes old. Thus they carry information to us undisturbed from the earliest moments of the Universe. The radio waves of the cosmic microwave background escaped and began their journey to us when the Universe was Gravitational waves escaped on a journey to us when the Universe was less than seconds old.
At longer periods. These are believed to form from the first massive stars born in our Universe. In this frequency range. Yet the signal from the quantum foam of the early Universe is still within reach.
Understanding the expansion history of the Universe at the moments when quantum foam was becoming our familiar space and time requires measuring the gravitational wave relics from this era at least two widely spaced frequencies. The Inflation Probe will search for the effects of waves with periods of billions of years. The goal of the Black Hole Imager mission will be to image directly matter falling into a black hole, with resolution comparable to the scale of the event horizon.
An angular resolution of 0. This resolution can be achieved at high radio frequencies and at X-ray wavelengths. A simple image, while exciting in concept, is not sufficient to study the dynamics of the inner regions. To better disentangle the complicated dynamics near the black hole will require spectroscopy to map the speed as well as position of gas as it nears the event horizon.
This will require spectroscopically resolved imaging at the wavelengths of X-ray lines. The science objectives for a black hole imaging mission are: Constellation-X takes a first step by demonstrating time-resolved spectroscopy of relativistically broadened X-ray lines but without the imaging capability of Black Hole Imager. The underlying mechanisms by which gas swirling into black holes loses energy are not well understood.
A direct image of the inner disk could reveal the details of this process. The ultimate irony of black hole accretion is that rather than swallowing everything, somehow many black holes manage to generate relativistic jets, by mechanisms that remain a mystery.
Imaging and spectroscopy will also provide direct tests of models that predict that magnetic fields extract energy from the black hole itself to power these jets. A simulated Black Hole Imager view of an accretion disk around a black hole.
The bending of light rays by the black hole makes the back side of the disk appear raised. Your feet arrive last. The Beyond Einstein program cannot succeed without investment in key enabling technologies for each mission. No mission can go into full flight development before it has achieved the appropriate level of technical readiness.
This requires a well-balanced technology program, in which both near- and long-term mission needs are addressed. Technology development for Beyond Einstein must be coordinated with other Space Science themes to identify cost sharing opportunities. Technology from early missions must be extended for later, more demanding missions. Scientists, the end-users of the technology, must be involved at all stages to ensure that mission requirements are met. Einstein Great Observatory Technologies Both Einstein Great Observatory missions have been under study for several years and have detailed technology roadmaps in place.
We highlight key elements below:. Constellation-X Constellation-X will provide X-ray spectral imaging of unprecedented sensitivity to determine the fate of matter as it falls into black holes, and map hot gas and dark matter to determine how the Universe evolved largescale structures.
Lightweight, grazing incidence X-ray optics. Each of the four identical Constellation-X spacecraft will carry two sets of telescopes: Both incorporate highly nested, grazingincidence X-ray mirror arrays, which must simultaneously meet tight angular resolution, effective area, and mass constraints. X-ray calorimeter arrays. Two technologies are being developed in parallel: Both have made substantial progress toward the required energy resolution of 2 eV.
Multiple approaches to fabrication of high-quality arrays and multiplexed readout amplifiers are under development. Long-lived 50mK coolers. Constellation-X requires reliable longlife first stage coolers operating at 5—10 K. The ultimate detector temperature of 50 mK will be reached by one of several adiabatic demagnetization refrigerator technologies currently under study.
Grazing incidence reflection gratings. Reflection gratings dispersed onto CCDs provide imaging spectroscopy in the 0.
For Constellation-X, improvements to reduce weight and in To measure the properties of merging pairs of supermassive black holes requires good sensitivity down at least to Hz.
The measurement of the relative motion of these dragfree masses allows us to sense the passage of gravitational waves through the Solar System. It consists of a triangle of reference masses in solar orbit connected by a precision metrology system. At hard X-ray energies. A prototype mirror segment for Constellation-X being separated from the replication mandrel. The key technologies are those to 1 minimize external disturbances of the reference masses.
Novel event-driven CCDs have recently been developed that provide significant improvements in performance and robustness. Key requirements have been demonstrated but work is continuing on extending the response at low energies and reducing the effects of electron trapping. Solid-state hard X-ray imaging detectors. To use the capture of compact objects to map spacetime outside of supermassive black holes sets the sensitivity requirements at wave frequencies of — Hz.
Changes in the 5 X km test mass spacing must be measured to m. This will require an Einstein Probe technology development Gravitational reference units of the kind shown inset and here undergoing testing are at the heart of the LISA mission. Correction signals are sent to the thrusters by gravitational reference units GRUs.
Laser Measurement System. Technology Development for the Einstein Probes The Einstein Probe mission concepts will be competed in order to choose the best scientific and technical approaches to their goals. But orbital dynamics lead to changes in spacecraft spacing that can create a fringe rate as large as 15 MHz. This program will be an important validation of the critical disturbance reduction system components.
Readiness must be evaluated before each competition. All of the measurements planned for the three Einstein probe missions are technically challenging. Micronewton thrusters keep the spacecraft precisely centered about the masses. That requirement can be met by existing lasers and detection systems.
System Verification. This imposes stringent requirements on laser frequency stability. Disturbance Reduction System. The very large detector arrays are a serious challenge: Some particular mission concepts are already being studied for each of the Probe science areas. The U. This may sound small. Even for optimistic models. The primary mirror must have much lower cost and mass-per-unit-area and be developed faster than the HST primary.
If relativity were not taken into account. Inflation Probe The Inflation Probe aims to detect signatures of gravitational waves with wavelengths comparable to the size of the Universe produced by quantum fluctuations of spacetime during inflation. If relativity were not accounted for. At infrared wavelengths. At optical wavelengths. A mission capable of such observations requires a wide field of view telescope with about a 2-meter diameter mirror. It will do this by measuring the weak imprint they leave on the polarization of the cosmic microwave background.
A portable GPS receiver determines position by simultaneously receiving signals from atomic clocks on the GPS satellites. Global Positioning System. This program should be provided as early as possible to allow all of the promising approaches to each mission to be thoroughly vetted. Below we discuss the technology development required for these candidate concepts. The whole system would be utterly worthless for navigation!
All of these elements require substantial technology development.
The Cosmic Quest for the Theory of the Universe
It is an order of magnitude weaker than the polarization components pro To separate these foreground sources requires extraordinary sensitivity and angular resolution. A CdZnTe detector array seems the most likely candidate. To provide sufficient sensitivity. Although detailed designs for successor missions would be premature. The sensitivity required is roughly 20— times that of the HFI focal plane detector on Planck. Since reflective optics provide very limited fields of view at these high energies..
Other technical challenges include the need for cold optics at low cost and mK detector operating temperatures with very stable temperature control.
One possible solution consists of four separate interferometers. Source-by-source removal of this foreground is practical at wave periods of 0. Big Bang Observer The ultimate goal of a Big Bang Observer is to directly observe gravitational waves with sufficient sensitivity to observe the background due to the quantum fluctuations during inflation. Achieving such a vast increase in sensitivity requires significant advances: Such a survey instrument would need to be sensitive over an energy range of about 10— keV.
This must be accomplished in the face of a strong foreground of gravitational waves produced by all the binary stars and black holes in the Universe. Other technology problems arise in the areas of mask fabrication and data acquisition at high trigger rates. Here a W laser scalable to 30 kW is shown under test. Such a configuration imposes many technical challenges. This will require advances in mirror fabrication. Acceleration Noise. A significant improvement in strain sensitivity. This gravitational wave frequency band will not have been previously explored.
To provide scientific guidance and to reduce the risk associated with making such large technical advances in one step. A gravitational reference sensor with acceleration noise performance times lower than that planned for LISA is required. Black Hole Imager The goal of the Black Hole Imager is to enable direct imaging of the distribution and motion of matter in the highly distorted spacetime near the event horizon of a black hole.
An X-ray interferometer is naturally matched to this task. An X-ray interferometer with 0. Strain Sensitivity. At wavelengths near 1 nm. This will require angular resolution better than 0. This means that separate spacecraft are needed with highly controlled formation flying. Nominal requirements are: The Black Hole Imager makes use of X-ray interference lower left.
An advanced form of gyroscope may be needed. To reduce the risks associated with making such large technical advances as these in one step. Mirror figuring. Though grazing incidence relaxes the required surface figure accuracy. Sensing and controlling the orientation of the line joining the centers of the reflector and detector spacecraft is probably the greatest technology challenge.
Theoretical studies include conceptual and analytical theory. That survey recommended that support for theory be explicitly funded as part of each mission funding line. Theoretical studies of early Universe cosmology. Rigorous modeling is an important factor in reducing mission risk and evaluating competing mission strategies. Chapter 4. Studies and simulations of signal extraction in the presence of multiple.
Theoretical studies of Type Ia supernovae and other candidate systems for calibrating cosmic distances. Beyond Einstein explores to the boundaries of foundational knowledge as well as to the boundaries of spacetime. Some examples of necessary theoretical studies supporting Beyond Einstein are: Comprehensive simulation of black hole environments. Early Universe cosmology and phenomenology of quantum gravity. Theoretical work combining anticipated new results from particle theory and experiment with cosmology will be important to optimize the probe to test theories of dark energy.
Models of relativistic hydrodynamic flows in accretion disks. Similar foundational studies are needed for other candidate techniques for the Dark Energy Probe. This is required on the shape of the Universe from observaboth as a calibrating set for the hightions of the cosmic microwave background. The Inflation Probe. Detector technology for COBE. Supporting Ground-Based Research and Analysis Beyond Einstein missions also require specialized supporting ground-based programs.
If Type Ia supernovae are employed. In the same way. Ground-based cosmic microwave background polarization experiments will be essential preparation for the Inflation Probe. In the case of the Einstein Probes. Whatever technique is adopted. Programs supporting ground-based studies of this type are already underway with funding from the National Science Foundation and the Department of Energy.
As in the case of theory. Its quest to investigate the Big Bang. This latter goal. The missions and probes in the Beyond Einstein theme offer unique educational opportunities.
Chapter 5. The missions and research programs in Beyond Einstein will bring significant resources to this educational challenge. In addition. Education and Public Outreach Education. Students yearn for a deeper Another crucial area of opportunity is technology education. The fantastic requirements of a mission like LISA—which will measure an object being jostled by less than the width of an atom—provoke the kind of excitement and questioning that draws young people into science and technology in the first place.
Many states now require technology education in middle school.
New results from MAP. These are necessary topics for the education community as they are included in the National Science Education Standards. The Beyond Einstein missions will fill many of the needs for materials about the Big Bang.
It matches what scientists regard as fundamental results with the appropriate education curriculum in a manner that is more specific than those embodied in the standards.
The missions of Beyond Einstein address the space science content in the origin of the Universe. Journey to the Edge of Space and Time. Education and public outreach programs in the past have seen great success in telling the human side of planning. I am a homeschooler and this is so comprehensive. Thanks to an efficient network of partnerships throughout the education and outreach communities.
Outreach programs for the Beyond Einstein theme will build on these existing partnerships and programs. Imagine the Universe!. Educational products and programs on the science themes of Beyond Einstein are expected to be extremely popular.
Either directly or indirectly. Special emphasis is placed on the pre-college years. We know that the public clamors to be involved in this story. The Starchild Web site for elementary students was one of the first winners of the Webby award for Education. Links to teachers will be established early in the Beyond Einstein program so that the educational component can grow with the program. The pioneering missions in Beyond Einstein offer opportunities to see the impact of dealing with profound questions on those who work toward the answers.
OSS products and programs now reach virtually every avenue of public interest. Beyond Einstein missions will weave an ongoing story that is considered one of the most compelling in all science—a story that will form the raw material for museum exhibits.
Chandra X-ray Observatory image of the gas remnant of a supernova explosion. Most of your body mass comes from elements created in stars. Cassiopeia A. Understand the development of structure in the Universe. Research Focus Area 8. Science Objective 5. Discover how gas flows in disks and how cosmic jets are formed. Research Focus Area Discover how the interplay of baryons. Research Focus Area 9. Determine how. Explore the cycles of matter and energy in the evolving Universe.
Understand how matter. Science Objective 4. Identify the sources of gamma-ray bursts and cosmic rays. Explore the behavior of matter in extreme astrophysical environments. Eta Carinae suffered a giant outburst about years ago and now returns processed material to the interstellar medium. The Universe is governed by cycles of matter and energy. A huge. Fowler [Nobel Prize.
From gas to stars and back again. To understand how matter and energy are exchanged between stars and the interstellar medium. It is illuminated with the soft glow of nascent and quiescent stars.
The aim of the SEU theme is to understand these cycles and how they created the conditions for our own existence. The SEU portfolio includes missions that have revolutionized our understanding of the web of cycles of matter and energy in the Universe. Even as the Universe relentlessly expands. To understand the structure and evolution of the Universe.
Chapter 6. The Chandra X-ray Observatory has been notable in this regard. Interdependent cycles of matter and energy determine the contents of the Universe. But to unravel the interlinked cycles. The missions of Beyond Einstein can address some of the goals of the Cycles of Matter and Energy program. Our task includes uncovering the processes that lead to the formation of galaxies and their dark matter halos.
The accumulated products of these events become the material for new stars that form in the densest interstellar regions. What We Have Learned The cycles that we seek to understand are driven by stars and galaxies. Bringing it all Together These stars congregate. Massive stars create new elements—oxygen. As they run out of hydrogen fuel.
Stars of later generations. The SEU theme is committed to mapping the processes by which these stellar factories build up the Universe.
Lower-mass stars evolve more sedately. To explain this rich variety. We know that when the Universe was a much younger and more violent place.
Gaseous filaments at the top of a hot bubble of gas are being expelled into intergalactic space. SEU missions will trace their evolution from their origins in the early Universe to the intricate systems we find today. Before describing how we plan to proceed.
Engines of Change in an Evolving Universe Stars are the factories for new elements in the Universe and. The oldest of these stars show us that our Galaxy once lacked the heavy elements out of which planets and people are made. The signposts of this process are the quasars Fountains of new elements spraying into the Universe. Our Earth. For a star. Different parts of these cycles produce radiation of different wavelengths. If the night were void of stars. But we can do this in at least three ways.
We can study nearby galaxies still under construction today. Even relatively quiet galaxies like our own have massive black holes lurking at their centers. Glimmers of secrets through the murk. The center of this galaxy is clearly revealed at infrared wavelengths. On Earth. And we can use powerful telescopes as timemachines to see the past directly: From space. The isolation of a space satellite also allows more stable and precise pointing. What role did black holes play in the evolution of galaxies?
It is a daunting challenge to try to understand events that happened billions of years ago in faraway places. We can measure the ages of stars in nearby galaxies to reveal their history of stellar births.
The Next Steps: The Space Astronomy Imperative Space-based telescopes are uniquely suited to uncovering the cycles of matter and energy in stars and galaxies. It also allows for cooling the telescopes.
For the farthest sources. With high spectral resolution these lines can be used to trace the flows of this gas in detail. The plan for the SEU theme takes three concerted approaches—cosmic censuses. We can use these spectral lines to measure redshifts and diagnose the radiating gas. The radiation in these lines rapidly cooled the interstellar clouds. The dust absorbed light and protected subsequent stellar nurseries from the damaging effects of ultraviolet light.
Metals such as gold and The Big Bang created only the lightest two elements. So the first generation of stars formed in warm. These clouds cooled because hydrogen molecules radiated their heat—at infrared wavelengths that can only be seen from space. Supernovae bright enough to observe directly are relatively rare. Cryogenic single-dish space telescopes will provide direct measurements of these lines and.
This was a key event. Most of the line radiation that cools collapsing gas clouds is not accessible to ground-based investments such as the Atacama Large Millimeter Array ALMA. The dust hides these nurseries from optical and ultraviolet instruments but is transparent to the infrared light that the dust emits. The carbon. To understand the consequences.
Details of a distant youth. But the rapidly expanding remnants they leave behind slowly cool and mix with the surrounding interstellar medium. A cryogenic. For this reason. The first solid particles. The infrared acuity of a space-based meter far-infrared telescope small yellow circles is superimposed on a simulated JWST image of distant extragalactic targets. Submillimeter interferometers in space will eventually offer detailed images.
The larger telescope will be able to pick out newly born galaxies at the edge of the Universe. The Explosive Enrichment of Galaxies The structure and evolution of the Universe is strongly driven by stellar collapse and explosive events.
Those that last longer than about one second are most likely associated with massive stars and corecollapse supernovae. We will build telescopes that will do this. A wide-field. A color composite of the supernova remnant E X-ray blue. These elements were created by nuclear reactions inside the star and hurled into space by the supernova. Gamma-ray line telescopes will also help studies of classical novae. Ground-based and space-based optical follow-up studies will supplement these efforts.
Recent technical advances offer increased sensitivity. The Chandra X-ray Observatory image shows. The X-ray data show that this gas is rich in oxygen and neon.
While the statistics are still sparse. An advanced Compton telescope that can see the radiation from these radioactive decays can be used to study the explosion mechanisms in core-collapse supernovae. E is the remnant of a star that exploded in a nearby galaxy known as the Small Magellanic Cloud. While pioneering efforts have come out of the Compton Gamma Ray Observatory.
Others may arise when a star is swallowed by a nearby black hole. Even in these smaller explosions. Radioactive elements are formed in detonation and core collapse supernovae. As a result. Studies of gamma-ray bursts GRBs have produced some of the most striking science of the last decade. Visions of new elements from a cosmic furnace. Most of the material of supernova remnants shines brightly with X-ray lines and Constellation-X will play an important role in determining their makeup: Cosmic rays provide another sample of material from the vicinity of supernova explosions.
The bursts are so bright that they can be seen even from the distant. Some gamma-ray bursts signal the death of a star and the birth of a black hole. Neutron stars offer extraordinary densities of matter and magnetic field strengths. Their physics determines how energy and matter are deposited throughout the Universe. These objects also allow observational access to extremes of density.
With a half-life of about a million years—short compared with the timescale of nucleosynthesis—the bright spots that concentrate in the inner galaxy must be contemporary sites of elemental enrichment. Neutron stars Revealing gravitational rogues inside galaxies. In this wide angle 1. Light and Wind from the Heart of the Beasts Beyond Einstein focuses on the physics of spacetime around compact objects and in the early Universe. Compact objects can be probed in many ways. Glowing embers of galactic nucleosynthesis.
Compact objects—white dwarfs. A cooling neutron star appears as a hot object in X-rays. Future telescopes will let us see nucleosynthesis happen. Unique processes. These cosmic laboratories test physics under extreme conditions that we cannot reproduce on Earth. The bright central source is probably due to a supermassive black hole in the nucleus of the galaxy.
Matter falling onto a neutron star from a binary companion also heats up and can ignite in thermonuclear explosions. Oscillations in the X-ray emission of compact objects reveal instabilities in the accretion disk and even the underlying Firing celestial beams of matter.
Diagram of AGN with warped disk. It is this vastly smaller scale that space interferometry will probe. The large improvement in spatial resolution of space radio interferometry over that from the ground allows the inner parts of nearby galactic accretion disks.
Note nonlinear scale. At right. Swirling disks of death around black holes. As the gas falls in. The gravitational energy liberated by the infall causes the central region of the disk to become fiercely luminous and it drives a jet of material outward along the polar axes of the galaxy.
The veil can be penetrated by infrared. In recent years. AGNs can be seen at very great distances. In this artist rendering. Because of their high luminosities.
These nuclear furnaces are often shrouded by the very dust and gas that provides the fuel for the beast. Quasars are active galactic nuclei AGN so bright that they outshine the surrounding galaxy. Peering into the hearts of galaxies. The evidence suggests that their radiation is produced by a supermassive black hole ingesting material from the galaxy surrounding it.
These studies will help us pin down the role black holes have played in the development of galaxies. Compact object studies reveal the activity of high-mass stars that produce the heavy elements required for life to form. Since the accretion disk is the supplier of fuel for compact objects. While it now seems to be accreting little matter. Though hidden from optical view by the disk of our Galaxy. While jets have now been observed throughout the electromagnetic spectrum.
New instruments from the Beyond Einstein program will help us study the innermost parts of the accretion disks of supermassive black holes. The full power of radio interferometry will not be realized until space-based telescopes provide longer baselines and shorter wavelengths.
A radio interferometry mission would resolve accretion disks around AGN out to almost Mpc and probe the inner disk that surrounds the closest supermassive black hole.
Did supermassive black holes form by merger of smaller ones. Accretion disks are also studied on larger scales using ground-based very long baseline interferometry VLBI. Such measurements would supplement the more complete dynamical picture provided by Constellation-X and the vision mission Black Hole Imager. Understanding how these jets are made. Constellation-X will study these galaxies in spectroscopic detail. This can map radio-emitting material in the accretion disk with a resolution over a hundred times finer than HST gets at visible wavelengths.
Such observations would help us design an eventual vision mission that could see even quiet galaxies at great distances and round out our picture of galaxy formation. Of special interest is the black hole that sits quietly at the center of our own Milky Way galaxy. Molecular maser lines would offer information about mass motions in the cooler.
As the closest massive black hole. This emission arises in the cool. We will locate the source and understand how it produces this extraordinary material. Low-resolution positron annihilation maps of the Milky Way made by the Compton Gamma-Ray Observatory reveal recognizable features from the disk and inner bulge of our Galaxy.
Large scale positron production is theoretically expected from black hole antimatter factories. They most likely arise from the detonation of a white dwarf that pulls so much mass off of a nearby companion that it collapses. Our Universe is asymmetric. We look ahead to building new low-energy gamma-ray telescopes designed specifically to search for annihilation radiation. But we cannot understand the evolution of their properties over cosmic times without modeling their nuclear burning and dynamics.
Positrons are formed by the decay of radioactive elements. By observing and modeling this radiation. These can be identified by their characteristic gamma-ray emission lines. Emission from compact sources could be highly transient.
With vastly higher spatial resolution and sensi- Detailed comparison of star formation in galaxies with active nuclei will be needed to investigate the roles that accretion disk-driven winds and point-like gravitational fields have on the formation of stars and the evolution of galaxies.
The origin of these positrons is unclear. The maps show that positrons are distributed on a Galaxy-wide scale. But they can also help us measure it! Type Ia supernovae are uniquely important in this regard because they are very bright and have roughly constant peak brightness. Such telescopes could detect all Type Ia supernovae out to at least the Virgo Group. We know that antimatter exists in the Universe.
An intensive hunt for such supernovae is under way and early results have led to the monumental realization that the expansion of our Universe is accelerating. In such an annihilation. While the search for antimatter can be conducted with cosmic-ray and gamma-ray experiments. Supernovae play a profoundly important role in the chemical enrichment of the Universe. A supernova of Type Ia can eject large quantities of newly formed radioisotopes. Visions of Annihilation Antimatter is being produced prodigiously in at least our own Galaxy.
These cosmic flash bulbs can thus be used to measure the large scale geometry of the Universe. Searching for sources of antimatter in a galactic forest. This is the highest resolution positron annihilation image available. Determining the nature of this non-baryonic dark matter is one of the central goals of modern physics and astronomy.
At top is the wealth of structure in the very center of this region as seen in three different parts of the spectrum. To keep their stars and hot gas from flying away. The Mystery of the Missing Matter According to the best cosmological models. Observing the center of our Galaxy will establish whether a burst of star formation there is responsible for driving a superwind laden with positrons and newly synthesized material. This montage illustrates our need for much more detailed images from new generation gamma ray telescopes to identify the sites and sources of antimatter in the inner galaxy.
The image of keV radiation from the Compton Gamma Ray Observatory is shown in the lower image and covers about 10 degrees of the sky around our Galactic Center.
These estimates still exceed the amount that we can actually see in stars and interstellar gas by a factor of ten. But the gravitational mass of the Universe is much larger still. We want to find this missing matter to understand why so little of it was used to build stars and galaxies. The fluctuations of the cosmic microwave background radiation are a powerful tool for assessing the total mass content of the Universe.
This polarization will reveal gravitational lensing by intervening matter. An efficient way to locate missing baryonic matter in the darkness of intergalactic space is to look for absorption of light from distant quasars. Making missing matter appear.
If the gas is hot and chemically enriched. By mapping this hot gas. A false-color X-ray image of the hot gas blue cloud taken by ROSAT is superimposed here on an optical picture of the galaxy group. The superstring theory. If correct, this means that the protons and neutrons in all matter, everything from our bodies to the farthest star. Nobody Ims seen these strings because they arc much too small to be Sllper. They are about billion billion times smaller than a proton.
According to the superstring theory, our world only appears to be made of point particles, because our measuring devices are too crude to see these tiny strings. At lirst it seems strange that such a simple concept-replacing point particles with strings-can explain the rieh diversity of partides and Drees which are created by the exchange of particles in nature. The superstring theory, however, is so elegant and comprehensive that it is able to explain simply why there can be billions upon billions of different types of particles and substances in the universe, each with astonishingly diverse characteristics.
Thc superstring theory can produce a coherent and all-inclusive picture of nature similar to the way a violin string can be used to "unite" all the musical tones and rules of harmony. Historically, the laws of music were formulated only after thousands of years of trialand-clTor investigation of different musical sounds. Today, these diverse rules can be derived easily from a single picture-that is, a stling that can resonate with different frequencies, each orie creating a separate tone of the musical scale.
The tones created by the vibrating string, such as C or B flat, are not in themselves any more fundamental than any other tone. What is fundamental, however. Knowing the physics of a violin string, therefore, gives us a comprehensive theory of musical tones and allows us to predict new harmonies and chords. The gravitational intcraction. Higher excitations of the string create different forms of matter.
From the point of view of the superstring theory. All particles are just different vibratory resonances of vibrating strings. Thus, a single framework-the superstring theory-can in principle explain why the universe is populated with such a rich diversity of particles and atoms.
The answer to the ancient question "What is malter'! The "music" created by the string is matter itscl f. But the fundamental reason why the world's physicists are so excited by this new tht:ory is that it appears to solve perhaps the most important scientific problem of the century: namely, how to unite the four forces of nature into one comprehensive theory.
At the center of this upheaval is the realization that the lour fundamental forces governing our universe are actually different manifestations of a single unifying force, governed by the superstring. Electricity is a force because it can make our hair stand on end. Over the last two thousand years, we grddually have realized that there arc four fundamental forces: gravity, electromagnetism light.
Other forces identified by the ancients, such as lire and wind, can be explained in terms or the four forces. One of the great scientific pllZl:les of our universe. For the past fifty years. To help you appreciate the excitement that the superstring theory is generating among physicists. Gravity is an attractive force that binds together the solar system. In our universe, gravity is the dominant lorce that extends trillions upon trillions of miles, out to the farthest stars; this force, which causes an apple to fall to the ground and keeps our feet on the floor, is the same torce that guides the galaxies in their motions throughout the universe.
The electromagnetic forcc holds together the atol It makes the electrons with negative charge orbit around the positively charged nucleus of the atom. Because the electromagnetic force determines the structure of the orbits of the electrons, it also governs the laws of chemistry.
S"perstr;ngs: A Theory of Everything? By rubbing a comb, for example, it is possible to pick up scraps of paper from a table. The electromagnetic force counteracts the downward force of gravity and dominates the other forces down to.
Perhaps the most familiar form of the electromagnetic force is light. When the atom is disturbed, the motion of the electrons around the nucleus becomes irregular.
This is the purest form of electromagnetic radiation, in the form of X rays, radar, microwave, or light. Radio and tclevision are simply different forms of the electromagnetic force.
Wlthm the nucleus of the atom, the electromab'lletic force is overpowered by the weak and strong nuclear forces. The strong force, for example, is responsible for binding together the protons and neutrons in the nucleus.
In any nucleus, all the protons arc positively charged. Left to themselves. The strong force, therefore, overcomes the repulsive force between the protons. Roughly speaking, only a few elements can maintain the delicate balance between the strong force which tends to hold the nucleus together and the repulsive electric loree which tends to rip apart the nucleus , which helps to explain why there are only about one hundred known elements in nature.
Should a nucleus contain more than about a hundred protons, even the strong nuclear force would have difficulty containing the repulsive electric force between them. When the strong nuelear force is unleashed, the effect can be catastrophic. For example. Pound for pound.
Indeed, the strong force can yield significantly more energy than a chemical explosive. The strong force also explains the reason why stars shine.
A star is hasically a huge nuclear furnace in which the strong force within the nueleus is unleashed. If the sun's energy, for example, were created hy burning coal instead of nuclear fuel, only a minuscule fraction of the sun's light would be produced. The sun would rapidly fizzle and 8 A Theory of the Universe turn into a cinder. Without sunlight, the earth would turn cold and life on it would eventually die. Without the strong force, therefore. If the strong force were the only force at work inside the nucleus, then most nuclei would be stable.
However, we know from experience that certain nuclei such as uranium, with ninety-two protons are so massive that they automatically break apart, releasing smaller fragments and debris, which we call radioactivity.
In these elements the nucleus is unstable and disintegrates. Therefore, yet another, weaker force must be at work, one that governs radioactivity and is responsible for the disintegration of very heavy nuclei.
This is the weak force. The weak force is so fleeting and ephemeral that we do not experience it directly in our lives. However, we feel its indirect effects. When a Geiger counter is placed next to a piece of uranium, the clicks that we hear measure the radioactivity of the nuclei, which is caused by the weak force. The energy released by the weak force can also be used to create heat.
For example, the intense heat found in the interior of the earth is partially caused by the decay of radioactive elements deep in the earth's core.
This tremendous heat, in tum, can erupt in volcanic fury ifit reaches the earth's surface. Similarly, the heat released by the core of a nuclear power plant, which can generate enough electricity to light up a city, also is caused by the weak force as well as the strong force.
Without these four forces, life would be unimaginable: The atoms of our bodies would disintegrate, the sun would burst, and the atomic fires lighting the stars and galaxy would be snuffed out.
The idea of forces, thcreforc, is an old and familiar one, dating back at least to Isaac Newton. What is new is the idea that these forces are nothing but different manifestations of a single force. Everyday experience demonstr,ltes the fact that an object can manifest itself in a variety of forms.
Take a glass of water and heat it until it boils and turns into steam. Water, normally a liquid, can turn into steam, a gas, with properties quite unlike any liquid. Now frecze the glass of water into ice.
By withdrawing heat. But it is still water- Superstrings: A Theory of Everything? Another, more dramatic example is the fact that a rock can turn into light. Under specific conditions, a piece of rock can turn into vast quantities of energy, especially if that rock is uranium, and the energy manifests itself in an atomic bomb.
Matter, then, can manifest itself in two forms either as a material object uranium or as energy radiation. In much the same way, scientists have realized over the past hundred years that electricity and magnetism are manifestations of the same force. Only within the last twenty-five years, however, have scientists understood that even the weak force can be treated as a manifestation of the same force. The Nobel Prize in was awarded to three physicists Steven Weinberg, Sheldon Glashow, and Abdus Salam who showed how to unite the weak and the electromagnetic forces into one force, called the "electro-weak" force.
Similarly, physicists now believe that another theory called the GUT, or "grand unified theory" may unite the electro-weak force with the strong interactions.
But the final torce gravity has long eluded physicists. In fact, gravity is so unlike the other forces that, for the past sixty years, scientists have despaired of uniting it with the others.
In some sense, these two theories are opposites: While quantum mechanics is devoted to the world of the very small such as atoms, molecules, protons, and neutrons relativity governs the physics of the very large, on the cosmic scale of stars and galaxies.
To physicists, one of the great puzzles of this century has been Ihat these two theories, from which we can in principle derive the sum total of human knowledge of our physical universe, should be HI A Theory of the Universe so incompatible. In fact, merging quantum mechanics with general relativity has defied all attempts by the world's greatest minds in this century. Even Albert Einstein spent the last three decades of his life on a futile search for a unifying theory that would include gravity and light.
Each of these two theories, in its particular domain, has scored spectacular successes. Quantum mechanics, for example, has no rival in explaining the secrets of the atom. Quantum mechanics has unraveled the secrets of nuclear physics. In fact, the theory is so powertul that, if we had enough time, we could predict all the properties of the chemical elements by computer, without ever having to enter a laboratory.
However, although quantum mechanics has been undeniably successful in explaining the world of the atom, the theory fails when trying to describe the gravitational force. On the other hand, general relativity has scored brilliant successes in its own domain: the cosmic scale of galaxies.
The black hole, which physicists believe is the ultimate state of a massive. General relativity also predicts that the universe originally started in a Big Bang that sent the galaxies hurtling away from one another at enormous speeds.
The theory of general relativity, however, cannot explain the behavior of atoms and molecules. It's as if nature created someone with two hands, with the right hand looking entirely different and functioning totally independently from the left hand.Eta Carinae suffered a giant outburst about years ago and now returns processed material to the interstellar medium.
He added. Of these. International participation is a key feature of Beyond Einstein. To describe everything about an isolated black hole. This energy transformed into the richly complex matter of which we and all we touch are made. We publish prepublications to facilitate timely access to the committee's findings.
If an eBook is available, you'll see the option to purchase it on the book page. Constellation-X and the Einstein Probes have attracted international interest that will be realized when the instruments are competitively selected. | 0.904297 | 3.162058 |
The nursery consequence refers to fortunes where the short wavelengths of seeable visible radiation from the Sun base on balls through a crystalline medium and are absorbed. but the longer wavelengths of the infrared re-radiation from the het objects are unable to go through through that medium. The caparison of the long wavelength radiation leads to more warming and a higher attendant temperature. Besides the warming of an car by sunshine through the windscreen and the namesake illustration of heating the nursery by sunshine go throughing through sealed. crystalline Windowss. the nursery consequence has been widely used to depict the caparison of extra heat by the lifting concentration of C dioxide in the ambiance. The C dioxide strongly absorbs infrared and does non let every bit much of it to get away into infinite.
A major portion of the efficiency of the warming of an existent nursery is the caparison of the air so that the energy is non lost by convection. Keeping the hot air from get awaying out the top is portion of the practical “greenhouse effect” . but it is common use to mention to the infrared caparison as the “greenhouse effect” in atmospheric applications where the air pin downing is non applicable.
Solar radiation at the frequences of seeable visible radiation mostly passes through the ambiance to warm the planetal surface. which so emits this energy at the lower frequences of infrared thermic radiation. Infrared radiation is absorbed by nursery gases. which in bend re-radiate much of the energy to the surface and lower atmosphere. The mechanism is named after the consequence of solar radiation go throughing through glass and warming a nursery. but the manner it retains heat is basically different as a nursery plant by cut downing air flow. insulating the warm air inside the construction so that heat is non lost by convection. Earth’s natural nursery consequence makes life as we know it possible. However. human activities. chiefly the combustion of fossil fuels and glade of woods. have intensified the natural nursery consequence. doing planetary heating
Greenhouse Effect Example
Bright sunshine will efficaciously warm a auto on a cold. clear twenty-four hours by the nursery consequence. The longer infrared wavelengths radiated by sun-warmed objects do non go through readily through the glass. The entrapment of this energy warms the inside of the vehicle. The caparison of the hot air so that it can non lift and lose the energy by convection besides plays a major function. Short wavelengths of seeable visible radiation are readily transmitted through the crystalline windscreen. Shorter wavelengths of ultraviolet visible radiation are mostly blocked by glass since they have greater quantum energies which have soaking up mechanisms in the glass. Even though one may be uncomfortably warm with bright sunshine streaming through. one will non be sunburned.
The Earth receives energy from the Sun in the signifier UV. seeable. and near IR radiation. most of which passes through the ambiance without being absorbed. Of the entire sum of energy available at the top of the ambiance ( TOA ) . about 50 % is absorbed at the Earth’s surface. Because it is warm. the surface radiates far IR thermic radiation that consists of wavelengths that are preponderantly much longer than the wavelengths that were absorbed ( the convergence between the incident solar spectrum and the tellurian thermic spectrum is little plenty to be neglected for most intents ) . Most of this thermic radiation is absorbed by the ambiance and re-radiated both upwards and downwards ; that radiated downwards is absorbed by the Earth’s surface. This caparison of long-wavelength thermic radiation leads to a higher equilibrium temperature. This extremely simplified image of the basic mechanism demands to be qualified in a figure of ways. none of which affect the cardinal procedure.
?The incoming radiation from the Sun is largely in the signifier of seeable visible radiation and nearby wavelengths. mostly in the scope 0. 2–4 ?m. matching to the Sun’s radiative temperature of 6. 000 K. Almost half the radiation is in the signifier of “visible” visible radiation. which our eyes are adapted to utilize. ?About 50 % of the Sun’s energy is absorbed at the Earth’s surface and the remainder is reflected or absorbed by the ambiance. The contemplation of light back into space—largely by clouds—does non much affect the basic mechanism ; this visible radiation. efficaciously. is lost to the system. ?The captive energy warms the surface. Simple presentations of the nursery consequence. such as the idealised nursery theoretical account. demo this heat being lost as thermic radiation. The world is more complex: the ambiance near the surface is mostly opaque to thermal radiation ( with of import exclusions for “window” sets ) . and most heat loss from the surface is by reasonable heat and latent heat conveyance. Radiative energy losingss become progressively of import higher in the ambiance mostly because of the diminishing concentration of H2O vapor. an of import nursery gas.
It is more realistic to believe of the nursery consequence as using to a “surface” in the mid-troposphere. which is efficaciously coupled to the surface by a oversight rate. ?The simple image assumes a steady province. In the existent universe there is the diurnal rhythm every bit good as seasonal rhythms and conditions. Solar heating lone applies during daylight. During the dark. the ambiance cools slightly. but non greatly. because its emissivity is low. and during the twenty-four hours the ambiance warms. Diurnal temperature alterations decrease with tallness in the ambiance. ?Within the part where radiative effects are of import the description given by the idealised nursery theoretical account becomes realistic: The surface of the Earth. warmed to a temperature around 255 K. radiates long-wavelength. infrared heat in the scope 4–100 ?m. At these wavelengths. nursery gases that were mostly crystalline to incoming solar radiation are more absorptive.
Each bed of ambiance with nurseries gases absorbs some of the heat being radiated upwards from lower beds. It re-radiates in all waies. both upwards and downwards ; in equilibrium ( by definition ) the same sum as it has absorbed. This consequences in more heat below. Increasing the concentration of the gases increases the sum of soaking up and re-radiation. and thereby farther warms the beds and finally the surface below. ?Greenhouse gases—including most diatomic gases with two different atoms ( such as C monoxide. CO ) and all gases with three or more atoms—are able to absorb and breathe infrared radiation. Though more than 99 % of the prohibitionist ambiance is IR transparent ( because the chief constituents—N2. O2. and Ar—are non able to straight absorb or breathe infrared radiation ) . intermolecular hits cause the energy absorbed and emitted by the nursery gases to be shared with the other. non-IR-active. gases.
The being of the nursery consequence was argued for by Joseph Fourier in 1824. The statement and the grounds was further strengthened by Claude Pouillet in 1827 and 1838. and reasoned from experimental observations by John Tyndall in 1859. and more to the full quantified by Svante Arrhenius in 1896.
WHAT ARE GREENHOUSE GASES?
Many chemical compounds present in Earth’s atmosphere behave as ‘greenhouse gases’ . These are gases which allow direct sunshine ( comparative shortwave energy ) to make the Earth’s surface unimpeded. As the shortwave energy ( that in the seeable and ultraviolet part of the spectra ) heats the surface. longer-wave ( infrared ) energy ( heat ) is reradiated to the ambiance. Greenhouse gases absorb this energy. thereby leting less heat to get away back to infinite. and ‘trapping’ it in the lower ambiance. Many nursery gases occur of course in the ambiance. such as C dioxide. methane. H2O vapour. and azotic oxide. while others are man-made. Those that are semisynthetic include the CFCs ( CFCs ) . HFCs ( HFCs ) and Perfluorocarbons ( PFCs ) . every bit good as sulfur hexafluoride ( SF6 ) . Atmospheric concentrations of both the natural and semisynthetic gases have been lifting over the last few centuries due to the industrial revolution. As the planetary population has increased and our trust on fossil fuels ( such as coal. oil and natural gas ) has been steadfastly solidified. so emanations of these gases have risen. While gases such as C dioxide occur of course in the ambiance. through our intervention with the C rhythm ( through combustion forest lands. or excavation and firing coal ) . we unnaturally move C from solid storage to its gaseous province. thereby increasing atmospheric concentrations.
Water Vapour is the most abundant nursery gas in the ambiance. which is why it is addressed here foremost. However. alterations in its concentration is besides considered to be a consequence of clime feedbacks related to the heating of the ambiance instead than a direct consequence of industrialisation. The feedback cringle in which H2O is involved is critically of import to projecting future clime alteration. but as yet is still reasonably ill measured and understood.
The natural production and soaking up of C dioxide ( CO2 ) is achieved through the terrestrial biosphere and the ocean. However. world has altered the natural C rhythm by firing coal. oil. natural gas and wood and since the industrial revolution began in the mid 1700s. each of these activities has increased in graduated table and distribution. Carbon dioxide was the first nursery gas demonstrated to be increasing in atmospheric concentration with the first conclusive measurings being made in the last half of the twentieth century. Prior to the industrial revolution. concentrations were reasonably stable at 280ppm.
Methane is an highly effectual absorber of radiation. though its atmospheric concentration is less than CO2 and its life-time in the ambiance is brief ( 10-12 old ages ) . compared to some other nursery gases ( such as CO2. N2O. Chlorofluorocarbons ) . Methane ( CH4 ) has both natural and anthropogenetic beginnings. It is released as portion of the biological procedures in low O environments. such as in swamplands or in rice production ( at the roots of the workss ) . Over the last 50 old ages. human activities such as turning rice. raising cowss. utilizing natural gas and excavation coal have added to the atmospheric concentration of methane.
Ultraviolet radiation and O interact to organize ozone in the stratosphere. Existing in a wide set. normally called the ‘ozone layer’ . a little fraction of this ozone of course descends to the surface of the Earth. However. during the twentieth century. this tropospheric ozone has been supplemented by ozone created by human procedures. The exhaust emanations from cars and pollution from mills ( every bit good as firing flora ) leads to greater concentrations of C and N molecules in the lower ambiance which. when it they are acted on by sunshine. bring forth ozone. Consequently. ozone has higher concentrations in and around metropoliss than in sparsely populated countries. though there is some conveyance of ozone downwind of major urban countries.
Concentrations of azotic oxide besides began to lift at the beginning of the industrial revolution and is understood to be produced by microbic procedures in dirt and H2O. including those reactions which occur in fertiliser incorporating N. Increasing usage of these fertilisers has been made over the last century
Chlorofluorocarbons ( CFCs ) have no natural beginning. but were wholly synthesized for such diverse utilizations as refrigerants. aerosol propellents and cleaning dissolvers. Their creative activity was in 1928 and since so concentrations of Chlorofluorocarbons in the ambiance have been lifting. Due to the find that they are able to destruct stratospheric ozone. a planetary attempt to hold their production was undertaken and was highly successful.
Carbon Monoxide and other reactive gases
Carbon monoxide ( CO ) is non considered a direct nursery gas. largely because it does non absorb tellurian thermic IR energy strongly plenty. However. CO is able to modulate the production of methane and tropospheric ozone. The Northern Hemisphere contains approximately twice every bit much CO as the Southern Hemisphere because every bit much as half of the planetary load of CO is derived from human activity. which is preponderantly located in the NH.
Volatile Organic Compounds ( VOCs ) besides have a little direct impact as nursery gases. every bit good being involved in chemical procedures which modulate ozone production. VOCs include non-methane hydrocarbons ( NMHC ) . and oxygenated NMHCs ( eg. intoxicants and organic acids ) . and their largest beginning is natural emanations from flora. However. there are some anthropogenetic beginnings such as vehicle emanations. fuel production and biomass combustion. Though measuring of VOCs is highly hard. it is expected that most anthropogenetic emanations of these compounds have increased in recent decennaries.
These are studies of the graphs produced in the IPCC 2007 study of the addition in cardinal nursery gases. They make clear that most of the addition of the last thousand old ages has occurred in the past 200 old ages. The radiative forcing of these gases is related to their concentration.
Role in clime alteration
Climate alteration will hold a significant impact on ecosystems and on human activities. Locally. the rise in temperatures has already triggered phenomena such as permafrost melt and lower H2O degrees in the Great Lakes and the St. Lawrence River. Experts besides predict that planetary heating will ensue in more utmost conditions. including more terrible snow storms. heat moving ridges. and drouths. Heat moving ridges are peculiarly worrisome in the Montreal country. In 2003. there were 69 heat-related deceases. and that figure is expected to increase by 80 % by 2050. The mean one-year figure of highly hot yearss in Montreal will lift from 13 to 55 during that same period.
The first United Nations environmental conference was held in Stockholm in 1972. Twenty old ages subsequently. the Earth Summit in Rio put environmental and development issues in the limelight. The United Nations Framework Convention on Climate Change ( UNFCCC ) . which was signed at that Summit. aimed to stabilise atmospheric GHG concentrations at a degree that would forestall any clime alteration. Convention signatories met in Kyoto In December 1997. and agreed upon a protocol aimed at cut downing GHG emanations in 38 industrialised states. between 2008 and 2012. to degrees averaging 5. 2 % lower than in 1990. Execution of this Protocol required confirmation by 55 of the sign language states that accounted for at least 55 % of the GHG emanations of industrialised states. The Kyoto Protocol took consequence on February 16. 2005. which was 90 yearss after Russia’s confirmation on November 16. 2004. THE GREENHOUSE EFFECT – CAUSES
The chief ground for nursery consequence is the emanation of gases like nitrous-oxide. carbon-di-oxide. methane. ozone and H2O vapor. The causes of these emanations have been listed below.
One of the major grounds for the nursery consequence is deforestation. With the addition in population. more and more woods are being cut to supply adjustment and other comfortss to people. This has led to an addition in the sum of C di-oxide in the ambiance. Add to this. combustion of woods. for the intent of deforestation. and we know why the C di-oxide has increased to such tremendous degrees.
II. Burning of Fossil Fuels
We all know that combustion of fossil fuels. like crude oil and oil. wood and gas consequences in release of pollutants into the ambiance. With clip. the ingestion of fossil fuels. be it for industrial intents or consumer intents. has increased and with it. the pollution degrees in the universe.
III. Electrical Appliances
Electrical contraptions are amongst the major subscribers to the nursery consequence. Refrigerators. air conditioners or some other electric contraptions emit gases. known as Chlorofluorocarbons ( CFCs ) . which have added to the nursery consequence.
Most of the industries today add to the pollution degrees and in bend. lead to the nursery consequence. Aerosol tins. some bubbling agents used in the packaging industry. fire asphyxiator chemicals and cleaners used in the electronic industry contribute to this. Even some procedures of the cement fabrication industries can be counted amongst the perpetrators.
Cars. whether they run on gasoline or Diesel. make pollution and release harmful gases into the ambiance. These gases. in bend. make the nursery consequence in the ambiance. The forever-increasing usage of cars has merely added to the job.
VI. Population Growth
The high rate of population growing has been indirectly responsible for the nursery consequence. With the addition in the figure of people. the demand for things like adjustment. apparels. autos. ACs. etc has increased. The consequence is more industries. more autos. more deforestation. and so on. The ultimate effect is greenhouse consequence.
THE GREENHOUSE EFFECT – IMPACT
The nursery effect‘s impact is to do life as we know it possible on planet Earth. but the nursery consequence may besides convey an terminal to life as we know it. The nursery consequence refers to the caparison of heat by certain gases in the ambiance. including C dioxide and methane. Although these gases occur in merely hint sums. they block important sums of heat from get awaying out into infinite. therefore maintaining the Earth warm plenty for us to last. Worlds have been adding nursery gases in inordinate sums to the ambiance of all time since the Industrial Revolution. which is heightening the nursery consequence and ensuing in what is now known as “global heating. ” This addition in nursery gases has the possible to do ruinous jobs for Earth and its dwellers.
I. The Biggest Problem – Sea Level Rise
The most unsafe facet of planetary heating is likely sea degree rise. In fact. the world’s oceans have already risen 4-8 inches. That may non sound like much. but it has been plenty to do the eroding of some islands. Peoples have had to relocate to higher land on low-lying islands in the South Pacific and off the seashore of India as a consequence of the effects of planetary heating. Further sea degree rise could do great agony. In Bangladesh entirely. there are 15 million people populating within 1 metre of sea degree and another 8 million in a similar circumstance in India. Inhabited land could be inundated if sea degrees continue to lift. Much of the world’s best farming area is low-lying. as are many of the world’s largest metropoliss. Even a really modest rise in sea degrees would hold an tremendous impact on 1000000s of people around the universe.
II. Droughts and Floods
Ironically. alterations in the clime due to extra nursery gases are doing both increased drouth and increased implosion therapy. Violent storm activity will increase as temperatures rise and more H2O evaporates from the oceans. This includes more powerful hurricanes. Pacific typhoons. and an increased frequence of terrible localized storms and twisters. As these storms frequently result in implosion therapy and belongings harm. insurance premiums are skyrocketing in coastal countries as insurance companies struggle to cover escalating costs. Warming besides causes faster vaporization on land. Many dry countries. including the American West. Southern Africa. and Australia are sing more terrible drouths. The sum of land on the Earth enduring from drought conditions has doubled since 1970. This has occurred even as entire planetary rainfall has increased by an estimated 10 % !
III. The Human Price of Climate Change
Drought is driving current additions in nutrient monetary values around the universe. in combination with increased usage of grains for fuel. Globally. the figure of malnourished people decreased up until the late ninetiess. Now that figure is increasing. Disease bearers will spread out their district. either by traveling to higher lifts in cragged countries or by spread outing their district farther from the equator. This enlargement will expose 1000000s of worlds to the frequently lifelessly infective diseases that these animate beings transmit. 150. 000 one-year deceases worldwide have been tied to climate alteration already. harmonizing to a 2005 World Health Organization study. Climate related deceases are expected to duplicate in 25 old ages. Industrialized states may be sheltered from the current impacts of clime alteration. but others are non. Heat moving ridges and drouths are responsible for these deceases. every bit good as inundations and more powerful storms linked to climate alteration.
IV. Approaching a Slippery Slope
Global temperatures have risen about. 8° Celsius or 1. 4° Fahrenheit already. As a consequence of this addition. the huge north-polar tundra is runing. let go ofing tremendous volumes of both C dioxide and methane into the ambiance. This creates the possibility of a self-reinforcing cringle of clime alteration: as more C dioxide and methane are released from the north-polar tundra. the nursery consequence will be farther enhanced. The world’s oceans are losing their ability to absorb C because of lifting H2O temperatures. harmonizing to roll uping grounds. This is important because the world’s oceans hold 50 times more C than do the world’s woods and grasslands. The diminishing capacity of the Earth’s C sinks to absorb C could further increase the likeliness of runaway clime alteration.
V. Rapid Climate Shifts
Scientists are going convinced that past rhythms of clime alteration on the Earth have been anything but slow and incremental. of all time since the thought that the Earth may warm over clip as a consequence of human-created clime alteration has reached the public consciousness. Climate alteration happens all of a sudden and violently. Research indicates that the Earth’s clime exists in a stable province for many 1000s of old ages. Then. force per unit area for alteration physiques from additions or lessenings in C degrees every bit good as alterations in solar radiation. At some point. the Earth reaches a tipping point where planetary clime systems and ocean currents are radically altered over the class of merely a few old ages. or even months. Once that threshold is crossed. the Earth’s clime goes through a period of dramatic disequilibrium. eventually settling down in a new stable province that is really different from the old 1. There is no turning back if we cross the threshold and make a tipping point. Weather patterns all over the universe may be disrupted. stoping life as we know it.
Greenhouse GASES AND GLOBAL Heating
There are legion environmental issues which threaten the really being of life on Earth. and planetary heating is possibly the most terrible of them all. Many people assume that the nursery consequence and planetary heating are one and the same thing. which is technically wrong. The high concentration of nurseries gases. such as C dioxide and methane. in the ambiance is one of the legion causes of planetary heating. That being said. the relationship between nursery gases and temperature rise can be best defined as cause and consequence relationship.
Difference between Greenhouse Gases and Global Warming
The term ‘greenhouse gases’ refers to assorted gases in the Earth’s ambiance. which are typically characterized by their ability to absorb infrared radiations coming from the Sun. The full procedure wherein the Sun’s infrared radiations are trapped within the ambiance by these nursery gases is referred to as the ‘greenhouse effect’ . Greenhouse gases list includes gases such as C dioxide. C monoxide. methane. CFCs. etc. . – some of which stay in the ambiance for several old ages and contribute to the nursery consequence on the planet. The atmospheric concentration of these gases is one of the chief causes of the nursery consequence. Global heating. on the other manus. refers to an ceaseless rise in planetary mean temperature triggered by assorted natural and anthropogenetic causes – nursery gases being one of them.
Relationship between Greenhouse Gases and Global Warming
Even though we say that the atmospheric concentration of nursery gases has a cardinal function to play when it comes to planetary heating. these gases are non the lone causes of this risky phenomenon. Other than the atmospheric concentration of these gases. planetary heating causes besides include legion other natural happenings and anthropogenetic activities. For case. solar radiations ( a natural cause ) and deforestation ( an anthropogenic cause ) are non at wholly related to nursery gases. but they do play a important function in doing the planetary temperature to lift. On the contrary. if it were non for these nursery gases. the Earth would hold been stop deading cold and devoid of any of the present life signifiers which inhabit it. The fact that these gases play a important function in keeping the necessary balance in planetary temperature makes their presence on the planet really of import.
If nursery gases are so of import. why are they blamed for planetary heating? Actually. the job arises when the sum of these gases in the Earth’s atmosphere exceeds the sum required to keep temperature balance. This addition in nursery gases atmospheric concentration consequences in pin downing of more infrared radiations within the Earth’s ambiance. and contributes to lift in planetary mean temperature. When it comes to natural causes of planetary heating that are closely related to greenhouse consequence – methane gas release is possibly the most outstanding one. Similarly. anthropogenetic causes of planetary heating which are associated with nursery consequence include – usage of vehicles. stationary beginnings such as industries. activities such as excavation and agricultural. etc.
While of course happening nursery gases have been playing the of import function of modulating the temperature on Earth since several centuries. those gases that are released as a consequence of human activities have changed the overall image. These nursery gases include C dioxide ( with a life-time of 200 old ages ) . azotic oxide ( 120 old ages ) . assorted CFC’s ( with their life-time runing between 5 – 1000 old ages ) and gases such as Perfluoropentane and Perfluorohexane ( with life-time transcending 1000 old ages ) .
CONCLUSION & A ; BIBLIOGRAPHY
These impacts of Greenhouse Effect are a dramatically pressing and serious job. We don’t need to wait for authoritiess to happen a solution for this job: each person can convey an of import aid following a more responsible life style: get downing from small. mundane things. It’s the lone sensible manner to salvage our planet. before it is excessively late. | 0.802857 | 3.446708 |
U-M leads $62M ‘largest radio telescope in space’ to improve solar storm warnings
ANN ARBOR—The most violent solar weather—coronal mass ejections—can flood space with high-energy particle radiation that would harm astronauts and damage spacecraft in its path.
A new $62.6 million NASA mission led by the University of Michigan aims to provide better information on how the sun’s radiation affects the space environment that our spacecraft and astronauts travel through.
The Sun Radio Interferometer Space Experiment, or SunRISE, consists of miniature satellites called cubesats that form a “virtual telescope” in space to detect and study the radio waves that precede major solar events. The waves can’t be detected on Earth’s surface due to interference from the region of Earth’s upper atmosphere known as the ionosphere.
SunRISE, expected to launch in 2023, will offer a never-seen-before glimpse at what goes on in the area above the sun’s surface, the solar corona. This region poses several long-standing mysteries for researchers.
“We can see a solar flare start, and a coronal mass ejection start lifting off from the sun, but we don’t know if it is going to produce high energy particle radiation, and we don’t know if that high energy particle radiation is going to reach Earth,” said Justin Kasper, U-M professor of climate and space sciences and engineering who leads the mission.
“One reason why is we can’t see the particles being accelerated. We just see them when they arrive at the spacecraft, which isn’t much of a warning.”
U-M will run the science operations center that converts the signals collected from the cubesats into images. Those images are expected to reveal which part of a coronal mass ejection (CME) is responsible for accelerating radiation particles outward.
Flying in a loose formation about six miles across, six cubesats will form the first imaging low frequency radio interferometer in space. The satellite constellation will orbit Earth slightly above geosynchronous orbit at five Earth radii, or 22,000 miles, from the surface.
“The cubesats will give us an entirely new view of how particles are accelerated near the sun and how they travel into interplanetary space by making the first images of the sky at very low radio frequencies from 20 Mhz to below 1 Mhz,” Kasper said. “The jury is still out on what accelerates the particles and where that acceleration occurs.
“It turns out the various theories about particle acceleration correspond to different parts of coronal mass ejections. So if we can see which part of the CME is glowing in radio, we figure out which acceleration model is right.”
Not all CMEs release high-energy particle radiation. During the peak period of the solar cycle, though, major ones that do happen every couple months. At their worst, these can include as much plasma and radiation as there is water in the Great Lakes—accelerating from rest to roughly 3 million miles per hour in tens of minutes.
Those events include several components—magnetized plasma from the sun itself, and the radiation. Both are threatening to Earth, not only to astronauts and spacecraft, but also to the electrical grid.
We have some ability to forecast when the magnetized plasma will hit Earth, since that component takes tens of hours or days to get here. But, as the radiation travels at near-light speed, there’s no way to predict when and where it will arrive.
Without understanding where CMEs produce intense particle radiation and whether a given CME is going to unleash a radiation event there is no time to respond to a major event before it arrives
“Knowing which part of a coronal mass ejection is responsible for producing the particle radiation will help us understand how the acceleration happens,” Kasper said. “It could also result in a unique warning system for whether an event will both produce radiation and release that radiation towards Earth or spacefaring astronauts.”
The bulk of that funding for the project will go toward payload and launch, while $5 million will go to U-M for its science team and operating costs. NASA’s Jet Propulsion Laboratory will manage the mission. Space Dynamics Laboratory, a nonprofit research corporation, is the other major partner that will build the spacecraft. U-M and JPL have partnered with MAXAR, a communications satellite company to launch and place the cubesats in their orbits.
The concept of utilizing a radio telescope in space is not a new one. But previous concepts for gathering this kind of data have been cost prohibitive. For example, it would be impossible to build and launch a 10-kilometer diameter dish into space.
SunRISE is one of NASA’s Missions of Opportunity, enabled through its Explorers Program, which provides flight opportunities for PI-led investigations from space. | 0.813528 | 3.699367 |
Spectrograph for INtegral Field Observations in the Near Infrared
Go to Unit Telescope 4 (UT4, Yepun) of the Very Large Telescope (VLT) at the Paranal Observatory and SINFONI can be found conducting its own beautiful observational orchestra, thanks to its two component instruments working together: SPIFFI (SPectrometer for Infrared Faint Field Imaging), which is an infrared integral field spectrograph, and the SINFONI-AO (adaptive optics) module. George Hau and Bin Yang are responsible for arranging SINFONI’s harmony with the stars.
An integral field spectrograph (IFS) allows you to observe in three dimensions across the entirety of an astronomical object in one go: each pixel of the image is associated with a full spectrum, measuring the intensity of the light at each wavelength (the wavelength is a measurement of its colour — in some objects, it can be converted into a velocity towards or away from the Earth and tells us about its relative position in space as a result.
SINFONI uses an “image slicer” technique: as shown in the figure below, a two-dimensional image (a) is chopped into smaller components (via “optical slicing”) and re-positioned by special segmented mirrors so that they lie in a line end-to-end instead of on top of each other (b). This essentially forms a very long virtual slit. The light from the virtual slit is split by SPIFFI into its separate colours and therefore wavelengths (c), and the image is then reconstructed from the individual slices at each wavelength, i.e. the image is reconstructed from all the slices at the red end of the spectrum, then the green, etc. They are then combined to give us the final, 3D information we desire (d).
Traditional methods of obtaining spectra over the full extent of a large, extended object is both time consuming and inefficient — an IFS solves both of these problems. SINFONI is therefore the ideal instrument for looking at some of the most interesting galaxies and planetary nebulae in the Universe. Because SINFONI only uses mirrors, it can be cooled to extremely low temperatures (between -150 and -273 degrees C, or “cryogenic temperatures”). This, combined with the adaptive optics module SINFONI-AO, which also works better towards the red end of the spectrum, means that overall SINFONI is tailored for observing at infrared wavelengths.
Thanks to SINFONI-AO, the instrument can also correct for atmospheric turbulence. The distorted image of a guide star is used to measure the effect of the turbulence, and a small, deformable mirror adjusts itself in real time to correct for these distortions. For the cases where a reference star is not available, the Laser Guide Star (LGS) can be used to create a bright spot 80 kilometres above the telescope and this is used as an artificial reference star. As a result, the images reaching SPIFFI are almost as sharp as if there were no atmosphere above the VLT at all — music to our ears!
Science highlights with SINFONI
- Discovery that early Universe galaxies were dominated by normal, rather than dark, matter (eso1709)
- Discovery of by far the brightest galaxy yet found in the early Universe and strong evidence found that examples of the first generation of stars lurk within it (eso1524)
- SINFONI was used to help reveal that three billion years after the Big Bang, giant eliptical galaxies still make stars in their outskirts, but no longer in their interiors (eso1516)
- Best view yet of dusty cloud (G2) passing galactic centre black hole (eso1512)
- SINFONI was used to gather the best direct observational evidence so far supporting the theory that galaxies pull in and devour nearby material in order to grow and form stars (eso1330)
- A giant gas cloud is being ripped apart by the supermassive black hole at the centre of the Milky Way; SINFONI has been studying the cloud’s fate (eso1151, eso1332). Before that, SINFONI observed the motion of stars surrounding the black hole, which were used to measure how far away it is and its mass. (eso0846).
- SINFONI has made many observations to study the growth and evolution of galaxies in a distant past: at the beginning, they tended to gently snack on nearby gas (eso1040, eso1330), but at a later stage in their growth, they would cannibalise other, smaller galaxies. (eso1212)
- The most distant galaxy ever measured to date was observed by SINFONI as it was only 600 million years after the Big Bang. (eso1041)
A raw image obtained with SINFONI. The image slicer chopped the image of a small region of the sky into a series of 32 narrow slices, and aligned them at the entrance of the spectrograph. The spectrograph then spread the light into its individual colours, forming a spectrum of each slice. Here, the 32 spectra of the individual slice appear as vertical bands. Each slice is slightly vertically offset from its neighbours. Complex data-processing software is required to re-assemble the information contained here into a full 3D spectral image.
The authoritative technical specifications as offered for astronomical observations are available from the Science Operation page. | 0.843623 | 3.996157 |
Earth’s dust cloud satellites confirmed
A team of Hungarian astronomers and physicists may have confirmed two elusive clouds of dust, in semi-stable points just 400,000 kilometres from Earth. The clouds, first reported by and named for Polish astronomer Kazimierz Kordylewski in 1961, are exceptionally faint, so their existence is controversial. The new work appears in the journal Monthly Notices of the Royal Astronomical Society.
The Earth-Moon system has five points of stability where gravitational forces maintain the relative position of objects located there. Two of these so-called Lagrange points, L4 and L5, form an equal-sided triangle with the Earth and Moon, and move around the Earth as the Moon moves along its orbit.
L4 and L5 are not completely stable, as they are disturbed by the gravitational pull of the Sun. Nonetheless they are thought to be locations where interplanetary dust might collect, at least temporarily. Kordylewski observed two nearby clusters of dust at L5 in 1961, with various reports since then, but their extreme faintness makes them difficult to detect and many scientists doubted their existence.
In a paper earlier this year the Hungarian team, led by Gábor Horváth of Eötvös Loránd University, modelled the Kordylewski clouds to assess how they form and how they might be detected. The researchers were interested in their appearance using polarising filters, which transmit light with a particular direction of oscillation, similar to those found on some types of sunglasses. Scattered or reflected light is always more or less polarised, depending on the angle of scattering or reflection.
They then set out to find the dust clouds. With a linearly polarising filter system attached to a camera lens and CCD detector at Judit Slíz-Balogh’s private observatory in Hungary (Badacsonytördemic), the scientists took exposures of the purported location of the Kordylewski cloud at the L5 point.
The images they obtained show polarised light reflected from dust, extending well outside the field of view of the camera lens. The observed pattern matches predictions made by the same group of researchers in an earlier paper and is consistent with the earliest observations of the Kordylewski clouds six decades ago. Horváth’s group were able to rule out optical artefacts and other effects, meaning that the presence of the dust cloud is confirmed.
Judit Slíz-Balogh comments on their discovery comments on their discovery: “The Kordylewski clouds are two of the toughest objects to find, and though they are as close to Earth as the Moon are largely overlooked by researchers in astronomy. It is intriguing to confirm that our planet has dusty pseudo-satellites in orbit alongside our lunar neighbour.”
Given their stability, the L4 and L5 points are seen as potential sites for orbiting space probes, and as transfer stations for missions exploring the wider Solar System. There are also proposals to store pollutants at the two points. Future research will look at L4 and L5, and the associated Kordylewski clouds, to understand how stable they really are, and whether their dust presents any kind of threat to equipment and future astronauts alike. | 0.916285 | 3.820428 |
The Kepler Space Telescope launched in 2009 was designed to detect and measure planetary bodies orbiting other stars. It was hoped that it would help slake the growing thirst for signs of alien but Earth-like worlds, extraterrestrial life and communications from other sentient beings. Results from the Kepler mission have, however, fostered a growing awareness that all is not well with the simple, Laplacian formation of planetary systems. For a start not one of the thousands of exoplanets revealed by Kepler is in a planetary system resembling the Solar System, let along sharing crucial attributes with the Earth. Giant planets occur around only a tenth of the stars observed, and even fewer in stable, near-circular orbits. Although it is early days in the quest for Earth- and Solar System look-alikes, some unexpected contrasts with the Solar System are emerging. For instance, many of the systems have far more mass in close orbit around their star, including gas giants with orbital periods of only a few days and giant rocky planets. Such configurations defy the accepted model for the Solar System where an outward increase in the proportion of volatiles and ices was thought to be the universal rule. Could these ‘hot Jupiters’ have formed further out and then somehow been dragged into scorching proximity to their star? Answers to this and other questions have been sought from computer simulations of the evolution of nebulas. Inevitably, the software has been applied to that of the Solar System, and the results are, quite literally, turning ideas about its early development inside out (Batygin, K., Laughlin, G. & Morbidelli, A., 2016. Born of chaos. Scientific American, v. 314(May 2016), p. 20-29).
It seems that at some stage in its growth from the protoplanetary disk the gravitational influence of a planet creates mass perturbations in the remainder of the disk. These feed back to the planet itself, to others and different parts of the disk to create complex and continuously evolving motions; individual planets may migrate inwards, outwards or escape their star’s influence altogether in a chaotic, unpredictable dance. Ultimately, some balance emerges, although that may involve the star engulfing entire worlds and other bodies ending up in interstellar space. It may also end up with worlds dominated by ‘refractory’ materials – i.e. rocky planets like Earth – orbiting further from their star than those composed of ‘volatiles’. In the case of the early Solar System the modelling revealed Jupiter and Saturn drifting inwards and dragging planetesimals, dust, ice and gas with them to create a gap in the protoplanetary disk. Within about half a million years the two giant planets became locked in their present orbital resonance, which changed the distribution of angular momentum between them and reversed their motion to outward. The clearing of mass neatly explains the asteroid belt and Mars’s otherwise inexplicably small size.
One of the characteristics emerging from Kepler’s discoveries is that ‘super Earths’ orbit close to their star in other systems. Had they existed in the early Solar System the inward drive of Jupiter and Saturn and their ‘bow wave’ of smaller bodies would have had consequences. Swarms of matter from the ‘bow wave’ captured and dissipated angular momentum from the super Earths and dissipated it within a few hundred thousand years, thereby pushing them into death spirals to be consumed by the Sun. This explains what by comparison with Kepler data is a mass deficit in the inner Solar System. The rocky planets – Mercury, Venus, Earth and Mars – accreted from the leftovers, perhaps over far longer periods than previously thought.
Intense bombardment of the Moon and the Earth took place during the first half billion years after they had formed, rising to a crescendo in its later stages. Formation of the mare basins brought it to a sudden close at 3.8 Ga, which coincides with the earliest evidence for life on Earth. Lunar evidence indicates that this Late Heavy Bombardment spanned 4.1 to 3.8 Ga. Previously explained by a variety of unsatisfying hypotheses it forms part of the new grand modelling of jostling among the giant planets. Once Jupiter and Saturn together with Uranus and Neptune had stabilised, temporarily, they accumulated lesser orbital perturbations from an outlying disk of evolving dust and planetesimals throughout the Hadean Eon. Ultimately, around 4.1 Ga, the giant planets shifted out of resonance, pushing Jupiter slightly inwards to its current orbit and thrusting the other 3 further outwards. Incidentally, this may have flung another giant planet out of solar orbit to the void. Over about 300 million years they restabilised their orbits through gravitational interaction with the Kuiper belt but at the expense of destabilising the icy bodies within it. Some fled inwards as a barrage of impactors, possibly to deliver much of the water in Earth’s oceans. By 3.8 Ga the giants had settled into their modern orbital set-up; hopefully for the last time. | 0.916781 | 3.987083 |
Mars is the fourth planet from the Sun and the second smallest (after Mercury), with a diameter of 6794 kilometers (53% of that of Earth). Mars is one of the four terrestrial planets (planets having a solid surface). If you were standing on Mars, you would weigh just 38% of what you weigh on Earth.
Mars orbits the Sun once every 1.8809 Earth-years, with an orbital eccentricity of 0.093—the greatest eccentricity of any planet except Mercury. It averages 1.52 times as far from the Sun as does Earth.
Mars rotates about its axis prograde (in the same direction as its solar orbit) once every 24 hours 37 minutes 23 seconds. This is closer to one Earth-day than the rotational period of any other planet. Its axis is tilted by 25.19° relative to the perpendicular of its orbital plane; this is closer to Earth's axial tilt of 23.45° than that of any other planet.
Scientists of 19th century believed that life had gained a toehold on Mars. Canals were discovered on the red planet by Italian astronomer, Giovanni Schiaparelli in 1887. These appeared as markings on the surface of Mars. Scientists believed that these canals are constructed by intelligent beings to divert water from polar regions to the desert areas. Like Earth, Mars had seasons. In spring and summer, the colour of the dark areas of the Mars changed from bluish green to yellow. So, it was suspected that plant life thrived on Mars. However, the Mars probe, Mariner 4 sent home pictures of a lifeless planet. Ultraviolet radiation from the sun coupled with the special nature of soil prevents Life from gaining on toehold on Mars.
Phobos is the larger and closer of Mars's two satellites, with a diameter of just 26 kilometers along one axis and just 18 kilometers along another axis. Of all the moons that are their planet's largest, Phobos is the smallest both in absolute terms and relative to its planet's size.
Deimos has a diameter of 16 kilometers along one axis and 10 kilometers along another. | 0.819144 | 3.17554 |
The planet, Kepler-1625 b, is likely more massive than Jupiter but in an Earth-like orbit around an old (9 billion years old) but otherwise Sun-like star. Discovered in 2016 among data from the Kepler Mission, the planet was subjected to an intense analysis by Teachey and Kipping as part of the Hunt for Exomoons with Kepler program. In spite of their persistence, Teachey and Kipping found only hints of a moonshadow accompanying the planet’s distinct transit signal.
Hoping to corroborate their putative moon, they applied for and received 40-hours to observe the system with the Hubble Space Telescope (HST) and look for more lunar transits. In these data, Teachey and Kipping found even more convincing evidence for a moon.
In the figure above, the little dip just to the right of the bigger dip (the planet’s transit) shows every sign of being the shadow of an exomoon circling a star about 7000 lightyears from Earth. Look around at how lucky we are to be alive right now.
Because of the extraordinary magnitude of their claim, Teachey and Kipping peppered their paper with lots of caveats, extending even to their paper’s title (“evidence for an exomoon”, not “we found a large exomoon”).
On top of that, they deployed an flotilla of statistical tests to argue in favor of the exomoon interpretation. One test in particular figures prominently in their analysis – the Bayes factor.
In this context, this ominous-sounding number is a measure of how much more likely one scientific model is over another, given a dataset. For instance, if you found your dog guiltily hiding from a mess in your house (your dataset), you would conclude there is a higher probability your dog made the mess (one scientific model) than a ghost did (another model).
The Bayes factor derives from work by the Rev. Thomas Bayes, a minister living in Georgian England, who developed a method to infer the underlying probability for a particular experimental outcome, given results from several actual experiments.
Later, the scientist Simon-Pierre Laplace developed Bayes’ work into a more general theory of inference that he hoped could be used, for example, by juries to judge the guilt or innocence of a defendant.
Nowadays, Bayesian inference shows up everywhere, from analyses of climate change to estimates of the frequency of orange Reese’s pieces. It’s even possible that our brains are natively wired as Bayesian-inference machines.
And so in deciding whether they’d found an exomoon, Teachey and Kipping compared the probability that their Hubble data arose from a model including a lunar transit (as well as gravitational tugs between a planet and moon) to the probability the data showed a lone transiting planet.
Although, as they caution, these probability estimates can’t account for everything, they find the planet-moon model is 400,000 times more probable than the planet-only model.
As always, more data are needed to corroborate this fantastic result, but if it holds up, Kepler-1625 would be a system with one super-sized Jupiter-like planet accompanied by a Neptune-sized moon which orbits at a distance of about 300,000 km, not too different from our own moon’s distance.
Very shortly after Teachey and Kipping’s work was published, Kollmeier and Raymond explored the question of whether this monster moon could have its own moon and found that even a moon as large as Ceres could remain stable.
This result immediately prompted a more pressing question: should we call such a body a “sub-moon” or “moonmoon”? | 0.860962 | 3.841197 |
The exploration of the outer Solar System has revealed a plethora of amazing worlds, the likes of which were little known or even unheard of just a decade ago. Among the most remarkable and tantalizing discoveries are the “ocean moons” such as Europa and Enceladus, which have oceans or seas of liquid water beneath their icy surfaces. Other moons like Titan, Ganymede, and Callisto may also have them, and even some asteroids. Titan also has seas and lakes of liquid methane/ethane on its surface. With all that water, these small worlds have become a primary focus in the search for possible life elsewhere in the Solar System. Now, a new NASA budget proposal wants to take that a step further and fund new missions to these watery moons.
The 2016 budget proposal from the U.S. House Appropriations Committee calls for the creation of an “Ocean Worlds Exploration Program” which would fund new missions to Europa, Enceladus, and Titan. From the proposal:
“Many of NASA’s most exciting discoveries in recent years have been made during the robotic exploration of the outer planets. The Cassini mission has discovered vast oceans of liquid hydrocarbons on Saturn’s moon Titan and a submerged salt water sea on Saturn’s moon Enceladus. The Committee directs NASA to create an Ocean World Exploration Program whose primary goal is to discover extant life on another world using a mix of Discovery, New Frontiers and flagship class missions consistent with the recommendations of current and future Planetary Decadal surveys.”
This is exciting news for those who have been advocating such missions. The bill provides $140 million to continue development of a new Europa mission, including a lander – $110 million more than requested. An additional $86 million goes toward developing new missions to Enceladus and Titan.
As Kevin Hand, a senior scientist at NASA’s Jet Propulsion Laboratory, noted: “The next few decades, if our exploration proceeds in a visionary manner, there are three key missions from the standpoint of searching for extant life. We should go to Europa and explore its subsurface ocean. We should land in the methane, and ethane lakes of Titan. And We should fly through and dive into the plumes of Enceladus.”
The bill also calls on NASA to launch the Europa mission by 2022; previously, NASA had only committed to a vague “mid-late 2020s.” The mission would utilize the Space Launch System (SLS) and may be a version of the previously proposed Europa Clipper, which would make repeated flybys of the moon. A lander, of course, would be a fantastic addition.
NASA’s Planetary Science Division receives $1.557 billion in funding overall, a very welcome announcement.
Jupiter’s moon Europa has long been of astrobiological interest to planetary scientists; a global water ocean lies beneath the outer icy crust, which is now thought to be quite similar to Earth’s oceans or soda lakes in salinity. New evidence suggests there is even sea salt on Europa’s surface. The rocky ocean floor could also provide nutrients and minerals for any putative life forms. With water, heat, and nutrients available, the Europan ocean is now considered to be one of the best places in the Solar System to search for life, even if only microbes. Even the darkest, deepest oceans on Earth are teeming with life.
More recently, Saturn’s moon Enceladus has been added to the water worlds list. The Cassini spacecraft found geysers of water vapour/ice crystals erupting from deep fissures in the moon’s icy surface at the south pole. They are now thought to originate from a subsurface ocean or sea of water, much like on Europa. There is also now evidence for hydrothermal activity on the ocean floor, much like on Earth. Cassini has already flown through and sampled the plumes directly, finding water vapour, ice crystals, salts, and organics. Cassini can’t identify living microbes in the plumes, but the data it has returned now makes Enceladus another place that scientists are keen to explore further.
Titan, Saturn’s largest moon, is very unique, with seas, lakes, rivers, and rain of liquid methane/ethane. It is much too cold for liquid water on the surface, but Cassini has also provided evidence for a subsurface ocean on this moon as well, although little else is known about it at this point. According to some scientists, it is also conceivable that some kind of primitive life could exist in the hydrocarbon seas and lakes, although it would be quite different than anything on Earth. Titan’s surface and atmosphere are both rich in organic material; even if there is no life, Titan is still considered to be a deep-freeze version of early Earth, with possible pre-biotic chemistry occurring which could provide clues to how life started on Earth.
All three of these moons provide a unique opportunity for exploration in the outer Solar System and could help to answer the question of how life arose on Earth and whether it exists anywhere else in the Solar System.
Another positive note is that the bill provides funding for both the Opportunity rover on Mars and the Lunar Reconnaissance Orbiter to continue after being faced with possible cancellation. As noted by Eric Berger, “This is a marvelous day for planetary science and the search for life.”
More information regarding the budget for planetary exploration overall is available here, and the budget in its entirety is here.
This article was first published on AmericaSpace. | 0.884198 | 3.054853 |
Nikhef scientists, together with colleagues from around the world, perform research at the Pierre Auger Cosmic Ray Observatory, an international observatory for the detection of ultra-high-energy cosmic radiation, located on the plains of western Argentina. They do so to learn more about the nature and origins of this mysterious cosmic radiation.
Each and every second, millions of cosmic rays pound the atmosphere, causing showers of subatomic particles. Low-energy particles wander about our Galaxy, often originating from the remnants of burnt-out stars after a supernova explosion. Ultra-high-energy particles are more rare and have energies of more than 100 million times the highest energy that can be generated on Earth using particle accelerators.
How does Nature accelerate particles to reach such extremely high energies? What particles does cosmic radiation consist of? Where do they come from? What happens during their ultra-high-energy collisions with Earth’s atmosphere? At the Pierre Auger Observatory in Argentina, an international collaboration of scientists looks for answers to these questions.
The Pierre Auger Observatory comprises several detectors:
- The particle detector consists of more than 1600 water tanks scattered over an area of 3000 square kilometres, where showers of secondary particles, caused by the impact of ultra-high-energy particles onto the atmosphere, are being detected.
- Whenever a shower of particles travels through the atmosphere, it also causes fluorescence. The light emitted in this way is detected by 27 highly sensitive telescopes that are located along the perimeter of the observatory and look at the sky above the area. This detector only works when it is completely dark, with no moon or clouds.
- New techniques are also being developed at the observatory, for example to detect the radio signals that result from the interaction of a shower of particles with the Earth’s magnetic field and the atmosphere.
Nikhef researchers and their colleagues at the Pierre Auger Observatory study particles with energies between 100 thousand TeV and 1 billion TeV, the highest energy investigated thus far.
By very carefully measuring the properties of a particle shower, the researchers determine where the cosmic radiation originated and which energy it has. They also work to reveal what the mass of the original cosmic ray is: is it as light as hydrogen, as heavy as iron, or somewhere in between?
By comparing the angles of incidence of the highest-energy radiation with the positions of known cosmic objects (black holes, galaxies, supernovae), they try to discover the origins of the cosmic radiation.
Together with international colleagues, Nikhef scientists develop detection stations for studying radio signals caused by the interaction of a particle shower with the Earth’s magnetic field and the atmosphere.
Research on a test set-up of almost 7 km2 has already proven to be successful: it was shown that the technique to determine the angle of incidence, energy, and nature of the incoming cosmic radiation by means of radio signals is comparable or even better than conventional techniques. Focus is currently being shifted to applying this knowledge towards measurements at a larger scale.
This research programme is a prime example of fundamental scientific research, aimed at gathering basic knowledge about everything around us. At the heart of this type of research is curiosity about what our Universe is made of and how it came to be. There’s much that we know already, for example that all visible matter is built up from atoms, yet many questions remain unanswered.
Fundamental research is not aimed at realizing applications in the short term. Still, one thing is for sure: no one can predict which ground-breaking applications will eventually emerge from this research. History shows that today’s fundamental knowledge forms the breeding ground for tomorrow’s discoveries. | 0.82925 | 4.11893 |
This image, made using images taken by NASA’s Dawn spacecraft during the mission’s High Altitude Mapping Orbit (HAMO) phase, shows Occator crater on Ceres, home to a collection of intriguing bright spots. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
The question on everyone’s mind about Ceres is what the heck are those bizarre bright spots discovered by NASA’s Dawn orbiter?
Since scientists believe that Ceres occupies a “unique niche” in the solar system and apparently harbors subsurface ice or liquid oceans, could the bright spots arise from subsurface “water leakage?” To find out Universe Today asked Dawn’s Principal Investigator and Chief Engineer.
“The big picture that is emerging is that Ceres fills a unique niche,” Prof. Chris Russell, Dawn principal investigator told Universe Today exclusively.
“Ceres fills a unique niche between the cold icy bodies of the outer solar system, with their rock hard icy surfaces, and the water planets Mars and Earth that can support ice and water on their surfaces,” said Russell, of the University of California, Los Angeles.
And with Dawn recently arrived at its second lowest science mapping orbit of the planned mission around icy dwarf planet Ceres in mid-August, the NASA spacecraft is capturing the most stunningly detailed images yet of those ever intriguing bright spots located inside Occator crater.
The imagery and other science data may point to evaporation of salty water as the source of the bright spots.
“Occasional water leakage on to the surface could leave salt there as the water would sublime,” Russell told me.
Dawn is Earth’s first probe to explore any dwarf planet and the first to explore Ceres up close. It was built by Orbital ATK.
To shed more light on what still remains rather mysterious even today, NASA has just released the best yet imagery, which was taken at Dawn’s High Altitude Mapping Orbit (HAMO) phase and they raise as many questions as they answer.
Occator has captured popular fascination world-wide because the 60 miles (90 kilometers) diameter crater is rife with the alien bodies brightest spots and whose nature remains elusive to this day, over half a year after Dawn arrived in orbit this past spring on March 6, 2015.
The new imagery from Dawn’s current HAMO mapping orbit was taken at an altitude of just 915 miles (1,470 kilometers). They provide about three times better resolution than the images captured from its previous orbit in June, and nearly 10 times better than in the spacecraft’s initial orbit at Ceres in April and May, says the team.
So with the new HAMO orbit images in hand, I asked the team what’s the latest thinking on the bright spots nature?
Initially a lot of speculation focused on water ice. But the scientists opinions have changed substantially as the data pours in from the lower orbits and forced new thinking on alternative hypotheses – to the absolute delight of the entire team!
“When the spots appeared at first to have an albedo approaching 100%, we were forced to think about the possibility of [water] ice being on the surface,” Russell explained.
“However the survey data revealed that the bright spots were only reflecting about 50% of the incoming light.”
“We did not like the ice hypothesis because ice sublimes under the conditions on Ceres surface. So we were quite relieved by the lower albedo.”
“So what could be 50% reflective? If we look at Earth we find that when water evaporates on the desert it leaves salt which is reflective. We know from its density that water or ice is inside Ceres.”
“So the occasional water leakage on to the surface could leave salt there as the water would sublime even faster than ice.”
At this time no one knows how deep the potential ice deposit or water reservoir sources of the “water leakage” reside beneath the surface, or whether the bright salt spots arose from past or current activity and perhaps get replenished or enlarged over time. To date there is no evidence showing plumes currently erupting from the Cerean surface.
Video Caption: Circling Occator Crater on Ceres. This animation, made using data from NASA’s Dawn spacecraft, shows the topography of Occator crater on Ceres. Credits: Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI
Dawn is an international science mission and equipped with a trio of state of the art science instruments from Germany, Italy and the US. They will elucidate the overall elemental and chemical composition and nature of Ceres, its bright spots and other wondrous geological features like the pyramidal mountain object.
I asked the PI and Chief Engineer to explain specifically how and which of the instruments is the team using right now at HAMO to determine the bright spots composition?
“The instruments that will reveal the composition of the spots are the framing camera [from Germany], the infrared spectrometer, and the visible spectrometer [both from the VIR instrument from Italy], replied Dr. Marc Rayman, Dawn’s chief engineer and mission director based at NASA’s Jet Propulsion Laboratory, Pasadena, California.
“Dawn arrived in this third mapping orbit [HAMO] on Aug. 13. It began this third mapping phase on schedule on Aug. 17.”
But much work remains to gather and interpret the data and discern the identity of which salts are actually present on Ceres.
“While salts of various sorts have the right reflectance, they are hard to distinguish from one another in the visible,” Russell elaborated to Universe Today.
“That is one reason VIR is working extra hard on the IR spectrum. Scientists are beginning to speculate on the salts. And to think about what salts could be formed in the interior.”
“That is at an early stage right now,” Russell stated.
“I know of nothing exactly like these spots anywhere. We are excited about these scientific surprises!”
Occator crater lies in Ceres northern hemisphere.
“There are other lines of investigation besides direct compositional measurement that will provide insight into the spots, including the geological context,” Rayman told Universe Today.
Each of Dawn’s two framing cameras is also outfitted with a wheel of 7 color filters, explained Joe Makowski, Dawn program manager from Orbital ATK, in an interview.
Different spectral data is gathered using the different filters which can be varied during each orbit.
“So far Dawn has completed 2 mapping orbit cycles of the 6 cycles planned at HAMO.”
Each HAMO mapping orbit cycle lasts 11 days and consists of 14 orbits lasting 19 hours each. Ceres is entirely mapped during each of the 6 cycles. The third mapping cycle just started on Wednesday, Sept. 9.
The instruments will be aimed at slightly different angle in each mapping cycle allowing the team to generate stereo views and construct 3-D maps.
“The emphasis during HAMO is to get good stereo data on the elevations of the surface topography and to get good high resolution clear and color data with the framing camera,” Russell explained.
“We are hoping to get lots of VIR IR data to help understand the composition of the surface better.”
“Dawn will use the color filters in its framing camera to record the sights in visible and infrared wavelengths,” notes Rayman.
“Dawn remains at HAMO until October 23. Then it begins thrusting with the ion propulsion thrusters to reach its lowest mapping orbit named LAMO [Low Altitude Mapping Orbit],” Makowski told me.
“Dawn will arrive at LAMO on December 15, 2015.”
That’s a Christmas present we can all look forward to with glee!
What is the teams reaction, interplay and interpretation regarding the mountains of new data being received from Dawn? How do the geologic processes compare to Earth?
“Dawn has transformed what was so recently a few bright dots into a complex and beautiful, gleaming landscape,” says Rayman. “Soon, the scientific analysis will reveal the geological and chemical nature of this mysterious and mesmerizing extraterrestrial scenery.”
“We do believe we see geologic processes analogous to those on Earth – but with important Cerean twists,” Russell told me.
“However we are at a point in the mission where conservative scientists are interpreting what we see in terms of familiar processes. And the free thinkers are imagining wild scenarios for what they see.”
“The next few weeks (months?) will be a time where the team argues amongst themselves and finds the proper compromise between tradition and innovation,” Russell concluded elegantly.
A batch of new results from Dawn at Ceres are expected to be released during science presentations at the European Planetary Science Congress 2015 being held in Nantes, France from 27 September to 2 October 2015.
The Dawn mission is expected to last until at least March 2016, and possibly longer, depending upon fuel reserves.
“It will end some time between March and December,” Rayman told me.
The science objectives in the LAMO orbit could be achieved as soon as March. But the team wants to extend operations as long as possible, perhaps to June or beyond, if the spacecraft remains healthy and has sufficient hydrazine maneuvering fuel and NASA funding to operate.
“We expect Dawn to complete the mission objectives at Ceres by March 2016. June is a the programmatic milestone for end of the nominal mission, effectively a time margin,” Makowski told Universe Today.
“The team is working to a well-defined exploration plan for Ceres, which we expect to accomplish by March, if all goes well.”
“At launch Dawn started with 45 kg of hydrazine. It has about 21 kg of usable hydrazine onboard as of today.”
“We expect to use about 15 kg during the nominal remaining mission,” Makowski stated.
Therefore Dawn may have roughly 5 kg or so of hydrazine fuel for any extended mission, if all goes well, that may eventually be approved by NASA. Of course NASA’s budget depends also on what is approved by the US Congress.
Dawn was launched on September 27, 2007 by a United Launch Alliance (ULA) Delta II Heavy rocket from Space Launch Complex-17B (SLC-17B) at Cape Canaveral Air Force Station, Florida.
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news. | 0.842208 | 3.59288 |
NASA on Sunday launched a probe that will head closer to the Sun than any other spacecraft before it. The Parker Solar Probe will endure wicked heat while zooming through the solar corona to study this outermost part of the stellar atmosphere that gives rise to the solar wind.
The Probe, a robotic spacecraft the size of a small car, was launched from Cape Canaveral in Florida, for its planned seven-year mission. It is set to fly into the Sun’s corona within 3.8 million miles or 6.1 million km from the solar surface, seven times closer than any other spacecraft.
The previous closest pass to the Sun was by a probe called Helios 2, which in 1976 came within 27 million miles or 43 million km. The average distance from the Sun for Earth is 93 million miles or 150 million km.
The corona gives rise to the solar wind, a continuous flow of charged particles that permeates the solar system.
Unpredictable solar winds cause disturbances in our planet’s magnetic field and can play havoc with communications technology on Earth. NASA hopes the findings will enable scientists to forecast changes in Earth’s space environment.
The project, with a $1.5 billion price tag, is the first major mission under NASA’s Living With a Star programme.
The probe is set to use seven Venus flybys over nearly seven years to steadily reduce its orbit around the Sun, using instruments designed to image the solar wind and study electric and magnetic fields, coronal plasma and energetic particles.
NASA aims to collect data about the inner workings of the highly magnetized corona. The probe, named after American solar astrophysicist Eugene Newman Parker, will have to survive difficult heat and radiation conditions.
It has been outfitted with a heat shield designed to keep its instruments at a tolerable 85 degrees Fahrenheit or 29 degrees Celsius even as the spacecraft faces temperatures reaching nearly 2,500 degrees Fahrenheit or 1,370 degrees Celsius at its closest pass. | 0.826429 | 3.173338 |
The Rosetta comet orbiter will meet a sticky end on 30 September, but not before a finale that should see it gather the most detailed images yet of 67P/Churyumov–Gerasimenko — or indeed of any comet.
In 2014, after a ten-year journey through deep space, Rosetta, operated by the European Space Agency (ESA), became the first craft ever to orbit a comet. Two years later, the orbiter is losing solar power as it speeds away from the Sun, and ESA scientists have opted to end the mission in style, with a controlled crash into the comet’s surface. “I love the idea that Rosetta will be resting on the comet surface for many thousands of years — it’s a fitting resting place for an amazing satellite,” says Laurence O’Rourke, an ESA astrophysicist and engineer.
Engineers at the European Space Operations Centre (ESOC) in Darmstadt, Germany, will set Rosetta on a collision course with the comet at around 20:50 utc on 29 September. The target is a 700-by-500-metre zone on the head of the rubber-duck-shaped comet, close to a 130-metre wide pit in a region named Ma’at, which is known for expelling gas and dust (see ‘Rosetta’s last hours’).
The crash site is around 2 kilometres away from the final resting place of Philae, the probe that landed in November 2014 but soon ran out of power. The trajectory of Rosetta's descent — a 13.5-hour freefall of around 19 kilometres — is designed to maximize sunlight and will not afford the orbiter a view of Philae. But the final flyby is expected to include spectacular images from elsewhere on the comet, perhaps as close as 15 metres from the surface and with resolution as high as mere millimetres per pixel. Rosetta has not previously been closer than 1.9 kilometres to its comet.
Rosetta scientists hope to use the cameras to see intriguing structures in the walls of the Ma'at pit that might hint at how comet 67P/Churyumov–Gerasimenko formed. Other instruments will chart gas, dust and ionized particles at an unprecedented range. “It’s a chance to get really unique science,” says Patrick Martin, mission manager for Rosetta. For the final images, Rosetta will have to race to send back precious data before it crashes seconds later. “It’s going to be really challenging,” adds Martin.
Resources are at a premium. At almost 575 million kilometres from the Sun, Rosetta is already operating on low power, and its increasing distance from Earth means that the speed with which it can transfer data is also dropping. To eke out the most science from the descent, scientists broadly agreed on which instruments would operate, with 3 of 11 teams volunteering to turn their instruments off, says Martin.
Rather than disintegrate on impact, the orbiter will perform a gentle crash-landing, striking the comet at a slow walking speed (around 1 metre per second) at 10:40 utc. But because Rosetta is not designed to land, even this could cause its 32-metre-wide solar-panel wings to snap, and the craft to tumble and bounce.
Exactly how Rosetta meets its end is likely to remain a mystery, because the craft will stop communicating with Earth after impact. The crash will trigger commands that shut down Rosetta even if the orbiter is intact, in order to comply with international regulations aimed at avoiding interference from deep-space network communication channels. (Even without this requirement, it's very unlikely that Rosetta, once crashed, would be capable of communication — because it will be unable to point its antenna in Earth's direction).
Rosetta’s distance from Earth means that news of the craft’s demise will come around 40 minutes after impact, when ESOC’s mission control expects to see Rosetta’s characteristic communication signal flat-line, at around 11:20 utc, or 13:20 local time. “For sure, it’s going to be a sad time for me,” says O’Rourke.
Rosetta's final hours will be live blogged by Nature’s news team.
- Journal name: | 0.821106 | 3.7372 |
By the end of this section, you will be able to:
- Explain how Copernicus developed the heliocentric model of the solar system
- Explain the Copernican model of planetary motion and describe evidence or arguments in favor of it
- Describe Galileo’s discoveries concerning the study of motion and forces
- Explain how Galileo’s discoveries tilted the balance of evidence in favor of the Copernican model
Astronomy made no major advances in strife-torn medieval Europe. The birth and expansion of Islam after the seventh century led to a flowering of Arabic and Jewish cultures that preserved, translated, and added to many of the astronomical ideas of the Greeks. Many of the names of the brightest stars, for example, are today taken from the Arabic, as are such astronomical terms as “zenith.”
As European culture began to emerge from its long, dark age, trading with Arab countries led to a rediscovery of ancient texts such as Almagest and to a reawakening of interest in astronomical questions. This time of rebirth (in French, “renaissance”) in astronomy was embodied in the work of Copernicus (Figure 2.16).
One of the most important events of the Renaissance was the displacement of Earth from the center of the universe, an intellectual revolution initiated by a Polish cleric in the sixteenth century. Nicolaus Copernicus was born in Torun, a mercantile town along the Vistula River. His training was in law and medicine, but his main interests were astronomy and mathematics. His great contribution to science was a critical reappraisal of the existing theories of planetary motion and the development of a new Sun-centered, or heliocentric, model of the solar system. Copernicus concluded that Earth is a planet and that all the planets circle the Sun. Only the Moon orbits Earth (Figure 2.17).
Copernicus described his ideas in detail in his book De Revolutionibus Orbium Coelestium (On the Revolution of Celestial Orbs), published in 1543, the year of his death. By this time, the old Ptolemaic system needed significant adjustments to predict the positions of the planets correctly. Copernicus wanted to develop an improved theory from which to calculate planetary positions, but in doing so, he was himself not free of all traditional prejudices.
He began with several assumptions that were common in his time, such as the idea that the motions of the heavenly bodies must be made up of combinations of uniform circular motions. But he did not assume (as most people did) that Earth had to be in the center of the universe, and he presented a defense of the heliocentric system that was elegant and persuasive. His ideas, although not widely accepted until more than a century after his death, were much discussed among scholars and, ultimately, had a profound influence on the course of world history.
One of the objections raised to the heliocentric theory was that if Earth were moving, we would all sense or feel this motion. Solid objects would be ripped from the surface, a ball dropped from a great height would not strike the ground directly below it, and so forth. But a moving person is not necessarily aware of that motion. We have all experienced seeing an adjacent train, bus, or ship appear to move, only to discover that it is we who are moving.
Copernicus argued that the apparent motion of the Sun about Earth during the course of a year could be represented equally well by a motion of Earth about the Sun. He also reasoned that the apparent rotation of the celestial sphere could be explained by assuming that Earth rotates while the celestial sphere is stationary. To the objection that if Earth rotated about an axis it would fly into pieces, Copernicus answered that if such motion would tear Earth apart, the still faster motion of the much larger celestial sphere required by the geocentric hypothesis would be even more devastating.
The Heliocentric Model
The most important idea in Copernicus’ De Revolutionibus is that Earth is one of six (then-known) planets that revolve about the Sun. Using this concept, he was able to work out the correct general picture of the solar system. He placed the planets, starting nearest the Sun, in the correct order: Mercury, Venus, Earth, Mars, Jupiter, and Saturn. Further, he deduced that the nearer a planet is to the Sun, the greater its orbital speed. With his theory, he was able to explain the complex retrograde motions of the planets without epicycles and to work out a roughly correct scale for the solar system.
Copernicus could not prove that Earth revolves about the Sun. In fact, with some adjustments, the old Ptolemaic system could have accounted, as well, for the motions of the planets in the sky. But Copernicus pointed out that the Ptolemaic cosmology was clumsy and lacking the beauty and symmetry of its successor.
In Copernicus’ time, in fact, few people thought there were ways to prove whether the heliocentric or the older geocentric system was correct. A long philosophical tradition, going back to the Greeks and defended by the Catholic Church, held that pure human thought combined with divine revelation represented the path to truth. Nature, as revealed by our senses, was suspect. For example, Aristotle had reasoned that heavier objects (having more of the quality that made them heavy) must fall to Earth faster than lighter ones. This is absolutely incorrect, as any simple experiment dropping two balls of different weights shows. However, in Copernicus’ day, experiments did not carry much weight (if you will pardon the expression); Aristotle’s reasoning was more convincing.
In this environment, there was little motivation to carry out observations or experiments to distinguish between competing cosmological theories (or anything else). It should not surprise us, therefore, that the heliocentric idea was debated for more than half a century without any tests being applied to determine its validity. (In fact, in the North American colonies, the older geocentric system was still taught at Harvard University in the first years after it was founded in 1636.)
Contrast this with the situation today, when scientists rush to test each new hypothesis and do not accept any ideas until the results are in. For example, when two researchers at the University of Utah announced in 1989 that they had discovered a way to achieve nuclear fusion (the process that powers the stars) at room temperature, other scientists at more than 25 laboratories around the United States attempted to duplicate “cold fusion” within a few weeks—without success, as it turned out. The cold fusion theory soon went down in flames.
How would we look at Copernicus’ model today? When a new hypothesis or theory is proposed in science, it must first be checked for consistency with what is already known. Copernicus’ heliocentric idea passes this test, for it allows planetary positions to be calculated at least as well as does the geocentric theory. The next step is to determine which predictions the new hypothesis makes that differ from those of competing ideas. In the case of Copernicus, one example is the prediction that, if Venus circles the Sun, the planet should go through the full range of phases just as the Moon does, whereas if it circles Earth, it should not (Figure 2.18). Also, we should not be able to see the full phase of Venus from Earth because the Sun would then be between Venus and Earth. But in those days, before the telescope, no one imagined testing these predictions.
Galileo and the Beginning of Modern Science
Many of the modern scientific concepts of observation, experimentation, and the testing of hypotheses through careful quantitative measurements were pioneered by a man who lived nearly a century after Copernicus. Galileo Galilei (Figure 2.19), a contemporary of Shakespeare, was born in Pisa. Like Copernicus, he began training for a medical career, but he had little interest in the subject and later switched to mathematics. He held faculty positions at the University of Pisa and the University of Padua, and eventually became mathematician to the Grand Duke of Tuscany in Florence.
Galileo’s greatest contributions were in the field of mechanics, the study of motion and the actions of forces on bodies. It was familiar to all persons then, as it is to us now, that if something is at rest, it tends to remain at rest and requires some outside influence to start it in motion. Rest was thus generally regarded as the natural state of matter. Galileo showed, however, that rest is no more natural than motion.
If an object is slid along a rough horizontal floor, it soon comes to rest because friction between it and the floor acts as a retarding force. However, if the floor and the object are both highly polished, the object, given the same initial speed, will slide farther before stopping. On a smooth layer of ice, it will slide farther still. Galileo reasoned that if all resisting effects could be removed, the object would continue in a steady state of motion indefinitely. He argued that a force is required not only to start an object moving from rest but also to slow down, stop, speed up, or change the direction of a moving object. You will appreciate this if you have ever tried to stop a rolling car by leaning against it, or a moving boat by tugging on a line.
Galileo also studied the way objects accelerate—change their speed or direction of motion. Galileo watched objects as they fell freely or rolled down a ramp. He found that such objects accelerate uniformly; that is, in equal intervals of time they gain equal increments in speed. Galileo formulated these newly found laws in precise mathematical terms that enabled future experimenters to predict how far and how fast objects would move in various lengths of time.
Sometime in the 1590s, Galileo adopted the Copernican hypothesis of a heliocentric solar system. In Roman Catholic Italy, this was not a popular philosophy, for Church authorities still upheld the ideas of Aristotle and Ptolemy, and they had powerful political and economic reasons for insisting that Earth was the center of creation. Galileo not only challenged this thinking but also had the audacity to write in Italian rather than scholarly Latin, and to lecture publicly on those topics. For him, there was no contradiction between the authority of the Church in matters of religion and morality, and the authority of nature (revealed by experiments) in matters of science. It was primarily because of Galileo and his “dangerous” opinions that, in 1616, the Church issued a prohibition decree stating that the Copernican doctrine was “false and absurd” and not to be held or defended.
Galileo’s Astronomical Observations
It is not certain who first conceived of the idea of combining two or more pieces of glass to produce an instrument that enlarged images of distant objects, making them appear nearer. The first such “spyglasses” (now called telescopes) that attracted much notice were made in 1608 by the Dutch spectacle maker Hans Lippershey (1570–1619). Galileo heard of the discovery and, without ever having seen an assembled telescope, constructed one of his own with a three-power magnification (3×), which made distant objects appear three times nearer and larger (Figure 2.20).
On August 25, 1609, Galileo demonstrated a telescope with a magnification of 9× to government officials of the city-state of Venice. By a magnification of 9×, we mean the linear dimensions of the objects being viewed appeared nine times larger or, alternatively, the objects appeared nine times closer than they really were. There were obvious military advantages associated with a device for seeing distant objects. For his invention, Galileo’s salary was nearly doubled, and he was granted lifetime tenure as a professor. (His university colleagues were outraged, particularly because the invention was not even original.)
Others had used the telescope before Galileo to observe things on Earth. But in a flash of insight that changed the history of astronomy, Galileo realized that he could turn the power of the telescope toward the heavens. Before using his telescope for astronomical observations, Galileo had to devise a stable mount and improve the optics. He increased the magnification to 30×. Galileo also needed to acquire confidence in the telescope.
At that time, human eyes were believed to be the final arbiter of truth about size, shape, and color. Lenses, mirrors, and prisms were known to distort distant images by enlarging, reducing, or inverting them, or spreading the light into a spectrum (rainbow of colors). Galileo undertook repeated experiments to convince himself that what he saw through the telescope was identical to what he saw up close. Only then could he begin to believe that the miraculous phenomena the telescope revealed in the heavens were real.
Beginning his astronomical work late in 1609, Galileo found that many stars too faint to be seen with the unaided eye became visible with his telescope. In particular, he found that some nebulous blurs resolved into many stars, and that the Milky Way—the strip of whiteness across the night sky—was also made up of a multitude of individual stars.
Examining the planets, Galileo found four moons revolving about Jupiter in times ranging from just under 2 days to about 17 days. This discovery was particularly important because it showed that not everything has to revolve around Earth. Furthermore, it demonstrated that there could be centers of motion that are themselves in motion. Defenders of the geocentric view had argued that if Earth was in motion, then the Moon would be left behind because it could hardly keep up with a rapidly moving planet. Yet, here were Jupiter’s moons doing exactly that. (To recognize this discovery and honor his work, NASA named a spacecraft that explored the Jupiter system Galileo.)
With his telescope, Galileo was able to carry out the test of the Copernican theory mentioned earlier, based on the phases of Venus. Within a few months, he had found that Venus goes through phases like the Moon, showing that it must revolve about the Sun, so that we see different parts of its daylight side at different times (see Figure 2.18.) These observations could not be reconciled with Ptolemy’s model, in which Venus circled about Earth. In Ptolemy’s model, Venus could also show phases, but they were the wrong phases in the wrong order from what Galileo observed.
Galileo also observed the Moon and saw craters, mountain ranges, valleys, and flat, dark areas that he thought might be water. These discoveries showed that the Moon might be not so dissimilar to Earth—suggesting that Earth, too, could belong to the realm of celestial bodies.
After Galileo’s work, it became increasingly difficult to deny the Copernican view, and Earth was slowly dethroned from its central position in the universe and given its rightful place as one of the planets attending the Sun. Initially, however, Galileo met with a great deal of opposition. The Roman Catholic Church, still reeling from the Protestant Reformation, was looking to assert its authority and chose to make an example of Galileo. He had to appear before the Inquisition to answer charges that his work was heretical, and he was ultimately condemned to house arrest. His books were on the Church’s forbidden list until 1836, although in countries where the Roman Catholic Church held less sway, they were widely read and discussed. Not until 1992 did the Catholic Church admit publicly that it had erred in the matter of censoring Galileo’s ideas.
The new ideas of Copernicus and Galileo began a revolution in our conception of the cosmos. It eventually became evident that the universe is a vast place and that Earth’s role in it is relatively unimportant. The idea that Earth moves around the Sun like the other planets raised the possibility that they might be worlds themselves, perhaps even supporting life. As Earth was demoted from its position at the center of the universe, so, too, was humanity. The universe, despite what we may wish, does not revolve around us.
Most of us take these things for granted today, but four centuries ago such concepts were frightening and heretical for some, immensely stimulating for others. The pioneers of the Renaissance started the European world along the path toward science and technology that we still tread today. For them, nature was rational and ultimately knowable, and experiments and observations provided the means to reveal its secrets.
Observing the Planets
At most any time of the night, and at any season, you can spot one or more bright planets in the sky. All five of the planets known to the ancients—Mercury, Venus, Mars, Jupiter, and Saturn—are more prominent than any but the brightest stars, and they can be seen even from urban locations if you know where and when to look. One way to tell planets from bright stars is that planets twinkle less.
Venus, which stays close to the Sun from our perspective, appears either as an “evening star” in the west after sunset or as a “morning star” in the east before sunrise. It is the brightest object in the sky after the Sun and Moon. It far outshines any real star, and under the most favorable circumstances, it can even cast a visible shadow. Some young military recruits have tried to shoot Venus down as an approaching enemy craft or UFO.
Mars, with its distinctive red color, can be nearly as bright as Venus is when close to Earth, but normally it remains much less conspicuous. Jupiter is most often the second-brightest planet, approximately equaling in brilliance the brightest stars. Saturn is dimmer, and it varies considerably in brightness, depending on whether its large rings are seen nearly edge-on (faint) or more widely opened (bright).
Mercury is quite bright, but few people ever notice it because it never moves very far from the Sun (it’s never more than 28° away in the sky) and is always seen against bright twilight skies.
True to their name, the planets “wander” against the background of the “fixed” stars. Although their apparent motions are complex, they reflect an underlying order upon which the heliocentric model of the solar system, as described in this chapter, was based. The positions of the planets are often listed in newspapers (sometimes on the weather page), and clear maps and guides to their locations can be found each month in such magazines as Sky & Telescope and Astronomy (available at most libraries and online). There are also a number of computer programs and phone and tablet apps that allow you to display where the planets are on any night. | 0.899073 | 3.859747 |
IN 2029 the inhabitants, if any, of the planet GJ 273b will receive a message that will change their lives forever. Encoded in radio signals emanating from an innocuous-looking blue-green planet 12.4 light-years away, will be tutorials in mathematics and physics, followed by a burst of music. The import of the message, however, will be clear: “Let’s talk.”
Or so Douglas Vakoch hopes. For on November 16th Messaging Extraterrestrial Intelligence (METI), the group that he heads, and the organisers of Sónar, a music festival in Barcelona, announced they had sent a series of missives towards Luyten’s star, the red dwarf around which GJ 273b orbits.
“Sónar Calling GJ 273b”, as the initiative is called, sent its message in mid-October from a radar antenna at Ramfjordmoen, in Norway. The antenna, run by EISCAT, a scientific organisation based at the Swedish Institute of Space Physics in Kiruna, is usually used to study Earth’s atmosphere. But EISCAT has form when it comes to messaging extraterrestrials. On June 12th 2008 the organisation beamed a 30-second advertisement for Doritos tortilla chips towards the constellation Ursa Major.
Dr Vakoch’s data were encoded in binary and sent on two frequencies, with a pulse in one frequency standing for “1” and the other for “0”. They include a count from one to five, mathematical operations like addition and multiplication, simple trigonometry and a description of electromagnetic waves. There is also a clock that counts the seconds that have passed since the transmissions began. That is the science.
The art comes courtesy of music from luminaries such as Jean-Michel Jarre. What GJ 273b’s inhabitants will make of the ten-second pieces, composed specially for the transmission, is unclear. But without them no message would have been sent, for Sónar is the one bankrolling the project in order to mark its 25th anniversary next year.
Nor is that the only anniversary. This week’s announcement coincides with the 43rd anniversary of the Arecibo message, a brief pictorial guide to humanity and the solar system, sent in 1974 from a giant radio telescope in Puerto Rico towards Messier 13, a cluster of stars some 25,000 light years away.
METI’s message is simpler than the Arecibo broadcast, and should, its senders hope, prove easier for its putative audience to decipher. The team hope to send more transmissions to the planet in April 2018, including a time when Earth will be listening for their reply: the northern hemisphere’s summer solstice in 2043. The team plans to send a similar message to thousands of other stars, in the hope of boosting the chances that at least one will find an audience.
Critics of such schemes argue that alerting the cosmos to humanity’s existence is a risky business. Dr Vakoch is not worried. He points out that it is in any case too late to keep quiet. An alien civilisation just a few hundred years more advanced than Earth’s would have the technology to detect the radio and television signals that human beings have inadvertently sent into space for decades.
This article appeared in the Science & technology section of the print edition under the headline "Nanoo nanoo" | 0.852608 | 3.040764 |
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