According to NASA's OSIRIS-REx, asteroid Bennu has a boulder-covered surface that protects it against small meteorite impacts.
Edward (Beau) Bierhaus, lead author of a paper published in this month's issue of Nature Geoscience, said that the observations give new insight into how asteroids respond to energetic impacts.
Bennu was formed from the debris of a larger asteroid that was destroyed by an impact. Bennu was formed from fragments from the collision.
The team used high-resolution global data sets to examine craters on Bennu.
A co-author of the paper said that measuring craters and their population on Bennu was very exciting. Something unique to small and rocky bodies was discovered at Bennu.
The age of the surface can be estimated by measuring the size and abundance of craters. The surface with the most impact craters is older than the surface with the least impact craters. Larger impactors are more likely to make larger craters. Small meteorites are more abundant than large meteorites, so they have more small craters.
The number of craters decreases as their size increases. As the size of the crater decreases, the number of craters decreases as well. Something strange is happening on Bennu.
The researchers believe that Bennu's boulders act as a shield, preventing small meteorites from forming craters. The impact is more likely to break apart the boulders. If Bennu's surface was covered in smaller, more uniform particles, impactors would make smaller craters than they do now.
The surface of Bennu is different because of this activity. One of the most rapid processes on a rubble-pile asteroid's surface is the displacement of a small group of boulders by a small impact. The surface on Bennu appears to be younger than the interior due to this.
More information: E. B. Bierhaus et al, Crater population on asteroid (101955) Bennu indicates impact armouring and a young surface, Nature Geoscience (2022). DOI: 10.1038/s41561-022-00914-5 Journal information: Nature Geoscience
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