Scientists have created some of the most vivid maps yet of the deepest and most mysterious spots beneath the ocean. Their effort, detailed in the Oct. 3, 2014, issue of the journal Science, has uncovered thousands of undersea mountains called seamounts that rise up from the seafloor. To create the seafloor map, which covers the world's oceans, the scientists relied on measurements taken from high-resolution altimeters onboard the European Space Agency's (ESA) CryoSat-2 satellite and NASA's Jason-1 satellite, along with information resulting from new data-processing methods. The results also shed light on seafloor tectonics, or the movements of massive oceanic plates that can shape the rifts, ridges and trenches decorating the ocean bottom. Here's a look at what the researchers uncovered. 
 
 The satellite altimeters worked by bouncing a radar signal or laser off the surface of the ocean being targeted and measuring how long it took the signal to return. That time can reveal the dips and peaks, or topography, of the ocean surface to within centimeters, scientists say. The sea-surface topography roughly mirrors changes in Earth's gravity. For instance, if an underwater volcano or mountain were hidden along the seafloor, the structure would push up against the sea surface and cause it to bulge. A trench, on the other hand, would cause the surface to sag. 
 
 Here, the result of a gravity model in the North Atlantic Ocean, with the red dots showing locations of magnitude-5.5 or greater earthquakes. The image also reveals seafloor spreading ridges and transform faults. (Photo Credit: David Sandwell, Scripps Institution of Oceanography) 
 
 A gravity-field image centered on the Indian Ocean, particularly at the Indian Ocean Triple Junction, where three major tectonic plates meet up: the African, Australian and Antarctic plates. This region of the ocean, the location of the crash site for the Malaysian Airlines aircraft lost on March 8, 2014, is poorly charted, the researchers noted. (Photo Credit: David Sandwell, Scripps Institution of Oceanography) 
 
 The gravity changes with depth in the North Atlantic were modeled to create this graphic that also shows seafloor-spreading ridges and faults. The gravity measurements reveal fracture zones on the ocean bottom that are currently veiled by sediment. (Photo Credit: David Sandwell, Scripps Institution of Oceanography) 
 
 A model of the changes in gravity with depth of the Southwest Indian ridge reveals fracture zones along the world's slowest spreading ridge. The fractures record rifting and spreading between Africa and Antarctica. (Photo Credit: David Sandwell, Scripps Institution of Oceanography) 
 
 A model of the changes in gravity with depth of the Mid-Atlantic Ridge, which is a boundary in Earth's surface where the Eurasian and North American tectonic plates scoot apart under the North Atlantic Ocean. The green dots indicate the locations of earthquakes of magnitude-5.5 and greater. (Photo Credit: David Sandwell, Scripps Institution of Oceanography) 
 
 Depths over seamounts and atolls of the South China Sea, derived from satellite altimeter gravity. The depths in shallow waters are improved by satellite images. (Photo Credit: Ministry of the Interior, Taiwan) 
 
 The gravity model reveals an extinct spreading ridge buried under sediment in the Gulf of Mexico, and the boundary between continental and oceanic crust (COB). (Photo Credit: David Sandwell, Scripps Institution of Oceanography) ||||| Image copyright Scripps Institution of Oceanography Image caption The new gravity data gives us our clearest view yet of the shape of the ocean floor 
 
 It is not every day you can announce the discovery of thousands of new mountains on Earth, but that is what a US-European research team has done. 
 
 What is more, these peaks are all at least 1.5km high. 
 
 The reason they have gone unrecognised until now is because they are at the bottom of the ocean. 
 
 Dave Sandwell and colleagues used radar satellites to discern the mountains' presence under water and report their findings in Science Magazine. 
 
 Image copyright Fugro Image caption Using ship-borne echosounders is expensive and time-consuming 
 
 "In the previous radar dataset we could see everything taller than 2km, and there were 5,000 seamounts," Prof Sandwell told BBC News. 
 
 "With our new dataset - and we haven't fully done the work yet - I'm guessing we can see things that are 1.5km tall. 
 
 "That might not sound like a huge improvement but the number of seamounts goes up exponentially with decreasing size. 
 
 "So, we may be able to detect another 25,000 on top of the 5,000 already known," the Scripps Institution of Oceanography researcher explained. 
 
 Media playback is unsupported on your device Media caption Dietmar Müller: We know much more about the topography of Mars than we know about the seafloor 
 
 Knowing where the seamounts are is important for fisheries management and conservation, because it is around these topographic highs that wildlife tends to congregate. 
 
 The roughness of the seafloor is important also as it steers currents and promotes mixing - behaviours that are critical to understanding how the oceans transport heat and influence the climate. 
 
 But our knowledge of the seafloor is poor; witness the problems they have had searching for the missing Malaysia Airlines jet MH370, which is believed to have crashed west of Australia. 
 
 Image copyright d.sandwell/Scripps Image caption Seeing fracture zones tells scientists about the movement of the continents 
 
 The problem is that saltwater is opaque to all the standard techniques that are used to map mountains on land. 
 
 Ship-borne echosounders can gather very high-resolution information by bouncing sound off bottom structures, but less than 10% of the global oceans have been properly surveyed in this way because of the effort it involves. 
 
 Dietmar Müller from the University of Sydney said: "You may generally think that the great age of exploration is truly over; we've been to all the remotest corners of continents, and perhaps one might think also of the ocean basins. But sadly this is not true - we know much more about the topography of Mars than we know about the seafloor." 
 
 Satellite observations 
 
 The alternative is an indirect method that uses satellites fitted with radar altimeters. 
 
 These spacecraft can infer the shape of the ocean bottom from the shape of the water surface above. 
 
 Because water follows gravity, it is pulled into highs above the mass of tall seamounts, and slumps into depressions over deep trenches. 
 
 Most of our maps of the gross outlines of mountains on the seafloor have relied on this approach. 
 
 Key advances were made using US Navy and European Space Agency satellites in the 80s and 90s. 
 
 Image copyright d.SANDWELL/scripps Image caption Gulf of Mexico: The jagged outline of an extinct spreading ridge is discernable 
 
 Now, Sandwell and his team have gathered new, improved datasets from more recent spacecraft - Jason 1, which was recently taken out of service, and CryoSat, which continues to orbit the Earth today. 
 
 Their denser coverage and better radar technologies have brought a two-fold improvement in the gravity model used to describe the ocean floor. 
 
 This richer information trove has barely been investigated yet, but already new discoveries are jumping out. 
 
 These include an extinct ridge where the seafloor spread apart to help open up the Gulf of Mexico about 180 million years ago. 
 
 And in the South Atlantic, the team sees the two halves of a different type of ridge feature that became separated roughly 85 million years ago when Africa rifted away from South America. 
 
 Image copyright Heriot-Watt University/JNCC/NERC Image caption Biodiversity and Conservation: It is around seamounts that wildlife tends to congregate 
 
 The striking thing is that many such structures are often covered by deep sediments and only become visible in the new gravity data. 
 
 Seeing all the major fracture zones in greater detail is sure to be a boon to those who study the history of Earth's shifting continents. 
 
 The team hopes to improve still the resolution of its model. 
 
 This will come as Cryosat continues to take more measurements in the years ahead. 
 
 The irony here is that the European Space Agency mission is really dedicated to tracing the shape and thickness of polar ice fields - not the shape of the seafloor. 
 
 Image copyright ESA Image caption CryoSat's primary role is to measure the shape of polar ice surfaces - not the shape of the seafloor 
 
 "CryoSat's orbit and payload were designed to meet its primary ice mission goals, and extending its coverage to the ocean was on a 'let's see what we get' basis," said principal investigator Duncan Wingham. "As it has turned out, we now have a marvellous new view of the ocean floor." 
 
 For its ice work, CryoSat works in a specific high-resolution mode, which could be extended to more areas of the ocean to garner improved seafloor data - if mission time allows. 
 
 Ultimately, though, researchers would like to see a dedicated mapper that was specifically tuned to the task. 
 
 Walter Smith, a co-author on Thursday's Science paper, proposed just such a mission in 2001 called ABySS. 
 
 It was not accepted then, but the National Oceanic and Atmospheric Administration scientist believes the case is still a compelling one. 
 
 "The miniaturization of computer chips and the increase in CPU processing speed and data storage in the last 13 years has made it easy and cheap to do amazing things with radar," he told BBC News. 
 
 "There is still a lot we could do with a dedicated mission. It could be done - everything, 'soup to nuts' - for 100 million Euros (£80m), and the necessary technological innovations are well known to radar engineers in England, France and elsewhere. It is just a question of political will to find the budget." 
 
 Interpolation of ocean-floor shape by satellite 
 
 Image copyright ESA 
 
 Most ocean maps are derived from satellite altimeter measurements 
 
 Satellites infer ocean-floor features from the shape of the sea surface 
 
 They detect surface height anomalies driven by variations in local gravity 
 
 The gravity from the extra mass of mountains makes the water pile up 
 
 In lower-mass regions, such as over trenches, the sea-surface will dip 
 
 Limited high-resolution ship data has calibrated the satellites' maps 
 
 Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos ||||| Accessing two previously untapped streams of satellite data, scientists at Scripps Institution of Oceanography at UC San Diego and their colleagues have created a new map of the world’s seafloor, creating a much more vivid picture of the structures that make up the deepest, least-explored parts of the ocean. Thousands of previously uncharted mountains rising from the seafloor and new clues about the formation of the continents have emerged through the new map, which is twice as accurate as the previous version produced nearly 20 years ago. 
 
 Developed using a scientific model that captures gravity measurements of the ocean seafloor, the new map extracts data from the European Space Agency’s (ESA) CryoSat-2 satellite, which primarily captures polar ice data but also operates continuously over the oceans, and Jason-1, NASA’s satellite that was redirected to map the gravity field during the last year of its 12-year mission. 
 
 Combined with existing data and drastically improved remote sensing instruments, the new map, described in the journal Science, has revealed details of thousands of undersea mountains, or seamounts, extending a kilometer or more from the ocean bottom. The new map also gives geophysicists new tools to investigate ocean spreading centers and little-studied remote ocean basins. 
 
 “The kinds of things you can see very clearly now are abyssal hills, which are the most common land form on the planet,” said David Sandwell, lead scientist of the paper and a geophysics professor in the Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics (IGPP) at Scripps. 
 
 The authors of the study say the map provides a new window into the tectonics of the deep oceans. Previously unseen features in the map include newly exposed continental connections across South America and Africa, and new evidence for seafloor spreading ridges at the Gulf of Mexico that were active 150 million years ago and are now buried by mile-thick layers of sediment. 
 
 “One of the most important uses of this new marine gravity field will be to improve the estimates of seafloor depth in the 80 percent of the oceans that remains uncharted or is buried beneath thick sediment,” the authors say in the report. 
 
 “Although CryoSat-2’s primary mission is in the cryosphere, we knew as soon as we selected its orbit that it would be invaluable for marine geodesy, and this work proves the point,” said Richard Francis, a coauthor of the paper and project manager for the development of CryoSat-2 at the European Space Agency, and honorary professor in the Department of Earth Sciences at University College London. 
 
 The new map also provides the foundation for the upcoming new version of Google’s ocean maps to fill large voids between shipboard depth profiles. 
 
 “The team has developed and proved a powerful new tool for high-resolution exploration of regional seafloor structure and geophysical processes,” says Don Rice, program director in the National Science Foundation’s (NSF) Division of Ocean Sciences. “This capability will allow us to revisit unsolved questions and to pinpoint where to focus future exploratory work.” 
 
 “The use of satellite altimeter data and Sandwell’s improved data processing technique provides improved estimates of marine gravity and bathymetry world-wide, including in remote areas,” said Joan Cleveland, Office of Naval Research (ONR) deputy director, Ocean Sensing and Systems Division. “Accurate bathymetry and identifying the location of seamounts are important to safe navigation for the U.S. Navy.” 
 
 In addition to Sandwell and Francis, coauthors of the paper include R. Dietmar Muller of the University of Sydney, Walter Smith of the NOAA Laboratory for Satellite Altimetry, and Emmanuel Garcia of Scripps. 
 
 The study was supported by NSF, ONR, the National Geospatial-Intelligence Agency, and ConocoPhillips.
– Underscoring how much of the Earth remains mysterious, scientists have located "thousands" of previously unknown underwater mountains, known as "seamounts," reports LiveScience. The discovery, announced in this month's Science journal, was a joint effort between a European Space Agency satellite and one from NASA that used high-tech imagery and gravity mapping to find the peaks, which rise a mile or more off the seafloor, the BBC reports. And because they're still analyzing the data, researchers think there may be even more of the topographical treasures. "We may be able to detect another 25,000 on top of the 5,000 already known," says one of the scientists involved with the project. The ocean's deepest parts remain a mystery—as evidenced by the logistical issues during the search for still-missing Malaysia Airlines Flight 370, as the BBC notes—but the Jason-1 and CryoSat-2 satellites worked together to bounce radar signals off the Earth to detect topographic "dips and peaks." The discovery is important to conservation scientists—"wildlife tends to congregate" near the mounts' peaks, notes the BBC—as well as to researchers who study seafloor makeup to determine water current and heat-transfer patterns. So how come we've never spotted the mountains before? A release from the Scripps Institution of Oceanography cites "drastically improved remote sensing instruments" and new data combined with old. "You may generally think that the great age of exploration is truly over; we've been to all the remotest corners of continents, and perhaps one might think also of the ocean basins," a University of Sydney professor tells the BBC. "But sadly this is not true—we know much more about the topography of Mars than we know about the seafloor." (Tons of plastic in the ocean seems to have disappeared, and that's probably not a good thing.)