APOD: 2020 September 16 - Gravel Ejected from Asteroid Bennu

Good morning, Rallypoint. Today's Astronomy Picture of the Day (APOD) is titled "Gravel Ejected from Asteroid Bennu." Asteroid Bennu currently has a visitor from Planet Earth: the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) spacecraft. Launched in September 2016, OSIRIS-REx is scheduled to retrieve a surface sample from Asteroid Bennu on October 20th and return that sample to Earth in 2023.

Beginning in 2019, scientists have studied a series of particle ejection events from the asteroid's surface. Comets are usually thought to be active (e.g. their dust and ion tails), but it turns out that some asteroids are as well. Watching through the eyes of OSIRIS-REx, researchers found that most of these pebble-size pieces of rock, typically measuring around a quarter-inch (7 millimeters), were pulled back to Bennu under the asteroid's weak gravity after a short hop, sometimes even ricocheting back into space after colliding with the surface. Others took longer to return to the surface, remaining in orbit for a few days and up to 16 revolutions. And some were ejected with enough oomph to completely escape from the Bennu environs.

Fun stuff -- watching the forces of creation still at work.

I'll post a video clip in a separate comment that animates a particle ejection events from 2019.