From the edge of the universe, we now jump to the surface of an asteroid near and dear to our hearts. Back on October 20, 2020, the OSIRIS-REx mission planned to gently boop the surface of the asteroid Bennu and grab a bit of rock as it bounced back away. Things didn’t exactly go as planned, and instead of a gentle boop, the spacecraft dramatically plunged into the surface before pulling away with more rock than it ever expected to pick up. 

Now, in a presentation from Dante Lauretta at the LPSC, we learned that plunge was a lot scarier than we knew. According to his abstract: Six seconds after making contact with the surface, the spacecraft fired its thrusters and initiated the backaway maneuver. At this point, the spacecraft still retained a downward velocity of ~4 cm/s. The backaway thrusters fired for 3 seconds before the downward velocity was arrested and the spacecraft began to safely move away from Bennu. At this point, the TAGSAM head had penetrated about 50 cm into the surface without much resistance. 

Put another way, by Paul Byrne on Twitter, the spacecraft would have continued meters into the asteroid if it hadn’t fired its gas canister. This asteroid is more the consistency of a pile of styrofoam balls on Earth. We are so lucky things went as they did, and I can’t wait to get those samples back to earth in September 2023.

More Information

The OSIRIS-REx Touch-and-Go Sample Acquisition Event and Implications for the Nature of the Returned Sample (LPSC abstract)