Before-and-after of asteroid Bennu’s sample site

As it made its final flyover of asteroid Bennu on April 7, 2021, NASA’s OSIRIS-REx spacecraft peered down to capture an image of the aftermath of its encounter with the asteroid, late last year. On its YouTube page, NASA compared the mark left by OSIRIS-REx on Bennu to “boot prints on the moon.” And, as you can see in the video above – and in the animation at the end of this post – the spacecraft did leave its mark when it touched down on asteroid Bennu and collected its sample on October 20, 2020.

Asteroid Bennu’s surface was altered in three ways by OSIRIS-REx. The first was the force of OSIRIS-REx’s touchdown, which disturbed the rocks and soil below. The second was the sampling mechanism blowing gas into a collection filter. The third was the spacecraft’s back-away thrusters as it kicked off Bennu’s surface, with its sample in tow.

OSIRIS-REx is the first NASA mission to visit a near-Earth asteroid and collect a sample to return to Earth. To achieve an “after” photo that compares to the March 2019 image, a team of scientists had to determine the best time and angle for the flyby. As Dathon Golish, a member of the OSIRIS-REx team at the University of Arizona, explained:

Bennu is rough and rocky, so if you look at it from a different angle or capture it at a time when the sun is not directly overhead, that dramatically changes what the surface looks like. These images were deliberately taken close to noon, with the sun shining straight down, when there’s not as many shadows. These observations were not in the original mission plan, so we were excited to go back and document what we did. The team really pulled together for this one last hurrah.

OSIRIS-REx will remain at Bennu until May 10, 2021, when it’ll begin its two-year-long return trip to Earth, with its precious cargo on board. Upon reaching Earth, the return sample will be jettisoned from the spacecraft in its own little pod called the Sample Return Capsule. The capsule will deploy a parachute in Earth’s atmosphere and land at the Utah Test and Training Range on September 24, 2023, if everything goes according to plan. Then scientists will be able to study the material from asteroid Bennu and learn more about the formation of our solar system.

Rocky surface with one rock circled in red, and red X in middle of slightly dark round area.
In the animation above, you can see Bennu’s surface before and after the OSIRIS-REx landing. The spacecraft acquired the first on March 7, 2019, and the second on April 7, 2021. See the red circle? It’s showing you a boulder that was blown 40 feet (12 meters) from its original spot on the asteroid’s surface, as OSIRIS-REx performed a touch-down maneuver that let it collect its sample on October 20, 2020. The red X in the after image targets the disturbed location where the spacecraft collected material. Image via NASA/ Goddard/ University of Arizona.

Bottom line: During its final flyby on April 7, 2021, the OSIRIS-REx spacecraft took an image of the location where it collected a sample from asteroid Bennu’s surface, more than a year ago. It’ll return to Earth two years from now to deliver its asteroid sample, so that scientists can learn more about the creation of our solar system.


April 17, 2021

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Kelly Kizer Whitt

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