By now, it's likely that you've heard about NASA's plans to send the unmanned Origins-Spectral Interpretation-Resource Identification-Security-Regolith Explorer (Osiris-REx) spacecraft on Sept. 8 to collect rock samples from Bennu, an asteroid estimated to measure 1,614 feet. If that's the case, then you've also likely heard reports about the asteroid having the potential to hit Earth and end all life here as we know it.
Well, as it turns out, that isn't quite true.
Yes, there is a chance that the asteroid will hit Earth in the last quarter of the 22nd century (a 0.037 percent chance, to be exact), but even if it does, mission officials noted that Bennu isn't close to being large enough to be an existential threat to the planet.
"We're not talking about an asteroid that could destroy the Earth," said Osiris-REx principal investigator 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."
What Is Bennu?
Bennu, classified as a potentially dangerous asteroid, was discovered in 1999 and named after an Egyptian mythological bird by a North Carolina third grader who won an asteroid-naming contest. As its classification might suggest, it is a prime example of a near-Earth object (NEO) — bodies in the Solar System whose orbits bring them close to Earth.
Bennu crosses the Earth's orbit every six years, and it gets closer every time. In fact, during a flyby in 2135, the asteroid could hit a special orbit-altering "keyhole" that could send it on a collision course with Earth later in the century.
Interestingly enough, NASA's mission has little to do with this less-than-likely collision. However, that doesn't mean it won't help. Osiris-REx will help scientists get a better understanding of Bennu's orbit, thus the odds of a collision — which is already well-known thanks to extensive research following its 1999 discovery. In fact, astronomers already pegged the astroid as having an orbital radius of about 20 feet.
"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."
What Is The Point Of The Mission?
Osiris-REx will be launched from a United Launch Alliance Atlas V rocket from Florida's Cape Canaveral Air Force Station on Sept. 8 and spend two years chasing Bennu down, before reaching it August 2018, with one primary objective in mind: spend two years on the NEO in order to study the asteroid from orbit, before collecting at least 2.1 ounces of surface material.
Expected to return by 2023, researchers will analyze the material in order to address several lingering questions — primarily how asteroids like Bennu contributed to the birth of life on Earth and the evolution of the Solar System. Scientists believe that the asteroid is rich in carbon, a key ingredient in the organic molecules that are needed for life. Organic molecules have been found in comet and meteorite samples, suggesting that some of the key ingredients of life can be created in space.
"Bennu's experiences will tell us more about where our solar system came from and how it evolved," said Edward Beshore, a member of the Osiris-REx mission. "Like the detectives in a crime show episode, we'll examine bits of evidence from Bennu to understand more completely the story of the solar system, which is ultimately the story of our origin."
There is also the planetary defense angle that was discussed previously, but as previously stated, it isn't the primary focus of the mission.
What If Bennu Does Hit Earth?
Even if Bennu manages to beat those one-in-2,700 odds and strikes the Earth, it would hardly deal the level of damage that various reports would have you believe.
There is no doubt that Bennu would utterly devastate the local area that it'd hit, but it couldn't wipe out civilization or cause a mass extinction. Why? Because, astronomers estimate that an asteroid capable of causing a global catastrophe would have to be at least 0.6 miles (3,168 feet). In comparison, Bennu is 1,614 feet — a little more than half of that. (for reference, the only asteroid confirmed to have caused — or at least contributed — to a mass extinction is believed to be about six miles in length).
With that said, if Bennu was found to be on a collision-course with Earth, there would still be a few options available. Given enough time, researchers say the asteroid could be veered off course via fly-along "gravity tractors" or "kinetic impactors." On the other hand, if we're pressed time, we still have nukes.
So, in the meantime, relax a little. Regardless of whether or not we have the means to tackle a collision (which we do), it's quite unlikely that anyone reading this will be alive long enough to see the situation play out.