How small particles could reshape Bennu and other asteroids

In January 2019, NASA's OSIRIS-REx spacecraft was orbiting 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 such particle ejection events have been observed at Bennu's surface.