spaceSpace and Physics

Asteroid Bennu’s Chance Of Hitting Earth Has Just Been Refined By NASA


Dr. Alfredo Carpineti

Senior Staff Writer & Space Correspondent

clockAug 12 2021, 13:05 UTC
This mosaic of Bennu was created using observations made by NASA’s OSIRIS-REx spacecraft taken over two years. Image Credit: NASA/Goddard/University of Arizona

This mosaic of Bennu was created using observations made by NASA’s OSIRIS-REx spacecraft taken over two years. Image Credit: NASA/Goddard/University of Arizona

NASA’s OSIRIS-REx mission to study asteroid Bennu was a resounding success. It orbited the asteroid, landed and collected samples to send home, and studied the space rock like never before. This mission matters because it helps us understand both the distant past of the Solar System but also the future of our planet, because one day Bennu could hit Earth.

OSIRIS-REx spent two years studying Bennu, one of the two most potentially hazardous known asteroids in the Solar System. These close-up observations have improved our understanding of the asteroid’s future orbit, which has in turn shrunk the uncertainty of the chance of a collision over the next few centuries, NASA revealed in a study published yesterday in the journal Icarus.


In 2135, Bennus will make a close approach to Earth. The chance that the asteroid will hit us is extremely low but it's important to continue monitoring it because close passages by our planet can change its orbit over time.

Before OSIRIS-REx, estimates had the chance of a Bennu impact sometime between 2175 and 2199 as 1 in 2,700. Thanks to the new data, the probability of an impact between now and the year 2300 is refined to about 1 in 1,750. The most likely date for an impact is September 24, 2182, and the impact probability for that specific day is 1 in 2,700. While that is a slightly higher risk than past estimates, it's still just a tiny change in an already low risk.

“The OSIRIS-REx data give us so much more precise information, we can test the limits of our models and calculate the future trajectory of Bennu to a very high degree of certainty through 2135,” lead author Davide Farnocchia, of the Center for Near-Earth Object Studies (CNEOS), which is managed by NASA’s Jet Propulsion Laboratory, said in a statement. “We’ve never modeled an asteroid’s trajectory to this precision before.”

During Bennu's close passage to Earth in September 2135, the asteroid won’t be a danger, but it will pass through certain “gravitational keyholes”, areas in space that will alter its trajectory towards Earth should it pass through them at certain times, due to Earth's gravitational pull. The team was able to refine that passage and in turn, improved the prediction of possible future impacts for centuries.

“NASA’s Planetary Defense mission is to find and monitor asteroids and comets that can come near Earth and may pose a hazard to our planet,” said Kelly Fast, program manager for NASA's Near-Earth Object Observations Program.

“We carry out this endeavor through continuing astronomical surveys that collect data to discover previously unknown objects and refine our orbital models for them. The OSIRIS-REx mission has provided an extraordinary opportunity to refine and test these models, helping us better predict where Bennu will be when it makes its close approach to Earth more than a century from now.”


And if Bennu does get too close there are already plans to push it off course. Both the US and China have considered ways to slowly nudge the asteroid away from Earth by hitting it with rockets.

 This Week in IFLScience

Receive our biggest science stories to your inbox weekly!

spaceSpace and Physics
  • tag
  • nasa,

  • asteroid