September 30, 2020
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How small particles could reshape Bennu and other asteroids – CU Boulder Today

Image of the asteroid Bennu with small bits of material jumping off into space.

OSIRIS-REx observed small bits of material leaping off the surface of the asteroid Bennu on Jan. 19, 2019. (Credit: NASA/Goddard/University of Arizona/Lockheed Martin)

In January 2019, NASA’s OSIRIS-REx spacecraft was orbiting the asteroid Bennu when the spacecraft’s cameras caught something unexpected: Thousands of tiny bits of material, some just the size of marbles, began to bounce off the surface of the asteroid—like a game of ping-pong in space. Since then, many more such particle ejection events have been observed at Bennu’s surface.

OSIRIS-REx is an unprecedented effort to investigate what makes up asteroids like Bennu and how they move through space. But, as those leaping particles show, the mission has already delivered a few surprises.

“We’ve been studying asteroids for a long time and no one had ever seen this phenomenon before—these little particles getting shot off of the surface,” said Daniel Scheeres, distinguished professor in the Ann and H.J. Smead Department of Aerospace Engineering Sciences. He leads the radio science team for OSIRIS-REx along with CU Boulder’s Jay McMahon.

Now, a series of new studies seeks to recreate and understand the observed particle ejection events, piecing together what happened and why. Scheeres and McMahon are focusing on one question in particular: How might the leaping particles change the long-term fate of Bennu and other asteroids like it?