Why Is Asteroid Bennu Ejecting Particles into Space?

by | Sep 10, 2020 | Asteroids, Bennu Mappers, Daily Space | 0 comments

Why Is Asteroid Bennu Ejecting Particles into Space?
IMAGE: This view of asteroid Bennu ejecting particles from its surface on Jan. 6, 2019, was created by combining two images taken by the NavCam 1 imager aboard NASA’s OSIRIS-REx spacecraft: a short exposure image, which shows the asteroid clearly, and a long-exposure image (five seconds), which shows the particles clearly. Other image-processing techniques were also applied, such as cropping and adjusting the brightness and contrast of each layer. CREDIT: NASA/Goddard/University of Arizona/Lockheed Martin

I can’t offer you much hope for this world, but I can tell you of another world, Bennu, and its compulsion to throw rocks. 

Back in January 2019, planetary scientists noticed particles catching the light as they flew away from this orbiting pile of rocks. In image after image, pebbles were seen hopping up and landing elsewhere or flying away altogether. These observed paths allowed some unexpected research to be completed! According to Steve Chelsey: The particles were an unexpected gift for gravity science at Bennu since they allowed us to see tiny variations in the asteroid’s gravity field that we would not have known about otherwise.

The source of these far-flung rocks remains a bit of a mystery. It looks like a combination of thermal fracturing and impacting meteors or one or the other of these effects may be providing the energy to launch pebbles into space. In the case of thermal fracturing, we’re looking at the constant heating and cooling of rocks causing them to actually break, and break with enough force to launch things. With meteorites, this is literally a case of space throwing rocks at Bennu, and those impacts causing Bennu to throw rocks back at space.

As a reminder, on October 20, the OSIRIS-REx mission will be attempting to steal rocks from Bennu, and we will bring that to you live on Twitch.tv/CosmoQuestX.

More Information

NASA Jet Propulsion Laboratory press release 

Southwest Research Institute press release 

Meteoroid Impacts as a Source of Bennu’s Particle Ejection Events,” W. F. Bottke et al., 2020 May 18, JGR Planets


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