Correction appended Aug. 3 
 
 On the off-chance you’re alive in 150 years, you could be in for a very bad day, when the asteroid Bennu collides with Earth, unleashing a blast 80,000 times more powerful than that of the bomb that destroyed Hiroshima. OK, the odds are pretty good you won’t be around in 150 years, and they’re only 1 in 2,700 at the very likeliest that Bennu will pay us such a nasty house call. But the space rock is making a lot of news and getting a lot of attention from NASA all the same—and it should. 
 
 Discovered in 1999, Bennu measures 1,614 ft. (492 m) across and checks two worrisome boxes on the asteroid danger list. It is what astronomers all a near-Earth object (NEO), which is any comet or asteroid that approaches the sun at 1.3 Earth’s distance or closer. Bennu not only gets that close but actually crosses Earth’s orbit every six years as it makes its own circuit through the solar system. It is also what is known as a potentially hazardous asteroid (PHA), which is any asteroid that measures 460 ft. (140 m) or more, is close enough to be an NEO and poses a risk of doing serious global or regional damage if it strikes Earth. A blast equivalent to 80,000 Hiroshimas is serious indeed. 
 
 But Bennu is less worrisome than it seems too. Here’s why. 
 
 For starters, in order to reach that 1 in 2,700 risk level in 150 years or so, the asteroid first has to be gravitationally nudged from its current course when it passes between Earth and the moon on an earlier approach it will make in 2135. That could happen: Gravity plays unpredictable tricks on moving bodies, and a body that passes between the gravitational fields of both Earth and the moon can be jostled in innumerable ways. Of course that also means Bennu might be pushed in a direction that makes it less rather than more likely to hit Earth in the future. 
 
 What’s more, asteroid tracking has become a very precise science—one that is led by NASA’s Near-Earth Objects Program Office at the Jet Propulsion Laboratory (JPL) in Pasadena. With the help of astronomers around the world, the JPL team has identified and mapped the route of 95% of the dangerous rocks in the solar system measuring 0.62 miles (1 km) or more, and 40% of those in the 460-ft. class. With the help of a bump in funding from Congress that was approved in 2012, JPL expects to get that second number up to 90%. 
 
 Knowing the course the space rocks take as they make their periodic swings through our cosmic neighborhood does a lot more than just let us know how long our species has to live before an incoming bit of ordnance sends us the way of the dinosaurs. It also means we can do something to prevent the disaster from happening at all. 
 
 Both NASA and the European Space Agency have gotten very good at visiting asteroids and comets. The ESA’s Rosetta spacecraft and Philae lander arrived at comet 67P in 2014 and NASA’s Dawn spacecraft is currently orbiting the dwarf planet Ceres after having already orbited the asteroid Vesta. Similar navigational skills could be used to launch interceptors to asteroids when they are still years away from reaching Earth. Once the spacecraft arrived at the target it could either break it apart with an explosive or, more prudently, simply push it off course either with an engine or simply by crashing into it. 
 
 NASA will get some practice soon with Bennu itself when it launches the OSIRIS-REx spacecraft on Sept. 8. Over the course of its seven-year mission, the probe will fly to Bennu, map its surface and return a small sample of its dust and other material to Earth for study. The mission should reveal more about the chemistry, history and the organic potential of the solar system generally and about Bennu’s composition specifically. The precise makeup of the asteroid could help scientists determine what it would take to destroy or deflect it if the need ever arises. 
 
 Until then though, as you were. Bennu may or may not be coming our way, but if it is, we’ve got plenty of time to prepare our hello. 
 
 Correction: An earlier version of this story misstated the impact of a collision by asteroid Bennu. It would be the equivalent of 80,000 Hiroshima bombs. ||||| NASA's new asteroid-sampling mission will do a lot of interesting things, but helping prepare humanity for Earth's imminent destruction is not among them. 
 
 There is indeed a chance that the 1,650-foot-wide (500 meters) asteroid Bennu — the target of NASA's OSIRIS-REx spacecraft, which is scheduled to launch next month — could hit Earth late in the 22nd century. 
 
 But, mission officials stressed, that chance is slim, and the space rock is not nearly big enough to pose an existential threat to the planet, despite what some media reports claimed over the weekend. [Potentially Dangerous Asteroids (Images)] 
 
 "We're not talking about an asteroid that could destroy the Earth," OSIRIS-REx principal investigator Dante Lauretta, of the Lunar and Planetary Laboratory at the University of Arizona, told Space.com. "We're not anywhere near that kind of energy for an impact." 
 
 If all goes according to plan, the $800 million OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer) mission will lift off atop a United Launch Alliance Atlas V rocket from Florida's Cape Canaveral Air Force Station on Sept. 8. 
 
 The spacecraft will spend two years chasing Bennu down, finally rendezvousing with the near-Earth asteroid in August 2018. OSIRIS-REx will then study the space rock from orbit for another two years before grabbing at least 2.1 ounces (60 grams) of surface material in July 2020. 
 
 In 2023, this relatively hefty sample should make it back to Earth, where researchers in laboratories around the globe will analyze the material in a number of ways. 
 
 The mission team is chiefly interested in learning the role that asteroids like Bennu — dark, primitive and apparently carbon-rich objects — may have played in helping life get a foothold on Earth, Lauretta said. 
 
 "Did these kinds of bodies deliver organic material and water, in the form of hydrated minerals like clays, to the surface of our planet that created the habitability and the environments that may have led to the origin of life?" Lauretta said. 
 
 "That's the prime mission," to investigate that question, he added. 
 
 There are secondary objectives as well, including learning more about the valuable resources that Bennu-like asteroids may harbor, Lauretta said. And then there's the planetary-defense angle, which has gotten a lot of attention in the last few days. 
 
 Bennu is officially classified as a potentially dangerous asteroid. In fact, there's an 0.037 percent (or 1-in-2,700) chance that it will strike Earth in the last quarter of the 22nd century, NASA scientists have calculated. 
 
 Specifically, that's the probability that, during an Earthy flyby in 2135, Bennu will hit a special orbit-altering "keyhole" that will send it on a collision course with the planet later in the century. 
 
 OSIRIS-REx will help scientists refine those odds, by refining their understanding of Bennu's orbit. (That orbit, by the way, is already the best-known of any asteroid, Lauretta said; thanks to extensive observations since Bennu's 1999 discovery, astronomers have nailed the space rock's orbital radius down to within 20 feet, or 6 m.) 
 
 "Our uncertainties will shrink, so that will allow us to recalculate the impact probability," Lauretta said. "We don't know which direction it'll go. It could go down, because we just eliminated a bunch of possible keyholes that Bennu may hit. Or it may go up, because in the area that's left we have a higher concentration of keyholes compared to the overall area of the uncertainty plane." 
 
 OSIRIS-REx's work will also help researchers better understand the Yarkovsky effect, which describes how absorbed sunlight, when radiated away as heat, affects an object's trajectory. Such information will improve knowledge not only of where Bennu is headed, but where it came from, Lauretta said. 
 
 But to focus on where it's headed — what if Bennu does hit one of those keyholes in 2135, and the space rock squares Earth up for an impact in 2185 or thereabouts? What should humanity expect? 
 
 Such an impact would likely devastate the local area but fall short of wiping out civilization or causing a mass extinction, experts have said. Astronomers estimate that a space rock must be at least 0.6 miles (1 kilometer) wide to cause a global catastrophe. (For perspective: The asteroid thought to have wiped out the dinosaurs — or at least to have finished them off — was probably about 6 miles, or 10 km, across.) 
 
 But an impact would not be inevitable, even if Bennu had Earth in its sights. Given a decade or so worth of lead time, researchers say, an incoming asteroid could potentially be nudged off course using fly-along "gravity tractor" probes and/or "kinetic impactors." And if time is not on humanity's side, there's always the nuclear option. 
 
 Follow Mike Wall on Twitter @michaeldwall and Google+. Follow us @Spacedotcom, Facebook or Google+. Originally published on Space.com.
– There's an asteroid out there that might slam into Earth in about 170 years, but contrary to some recent scary-sounding headlines, it won't wipe out Earthlings if it does, reports Space.com. "We're not talking about an asteroid that could destroy the Earth," says Dante Lauretta of the Lunar and Planetary Laboratory at the University of Arizona. "We're not anywhere near that kind of energy for an impact." In fact, the odds that asteroid Bennu will strike Earth are just 0.037%, a 1-in-2,700 chance, according to NASA calculations, which are expected to become more precise thanks to a new mission. OSIRIS-RE will lift off on Sept. 8 and spend two years hunting the asteroid, then study it for another couple years before bringing at least 2.1 ounces of its surface back to Earth in 2023. Questions will focus on, say, whether asteroids delivered organic matter to our planet, but the mission will also "allow us to recalculate the impact probability," Lauretta adds. The asteroid crosses our orbit every six years. If it hits a so-called "keyhole" when it passes by Earth in 2035, it would be put on track to collide with the Earth in 2185. Astronomers estimate that space debris has to be at least 0.6 miles wide to be seriously catastrophic; as a frame of reference, the asteroid believed to exterminate the dinosaurs was closer to 6 miles across. Bennu, which was first spotted in 1999 and is classified as a potentially hazardous asteroid, measures about 1,600 feet across, notes Time. (That asteroid that claimed dinos almost wiped out all mammals, too.)