Scientists saw something amazing in the images beamed back to Earth after OSIRIS-REx approached the asteroid Bennu. There were swarms of marble-sized rocks on the asteroid's surface.
A new study shows how asteroid activity happens. The pebbles that shoot off the asteroid can be pulled in by the space rock's gravity. There is a kind of cement of minerals from all around the asteroid's surface caused by another collision.
The first author of the new study is a graduate student at the Chicago Field Museum and the University of Chicago.
Astronomers used to think that asteroids had to undergo dramatic, high-speed, high-pressure collisions to change their surface.
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The new study shows that it doesn't take much to transform an asteroid. The researchers found this when they looked at a piece of the meteorite that fell in Costa Rica. Fragments of the space rock, which became a smooth glassy sheen as a result of the heating it experienced in the atmosphere, hit the roof of a house and a dog house.
There is a meteorite in Costa Rica. The dog is in good shape.
To break up the tiny minerals from the meteorite, we had to freeze it and thaw it with liquid nitrogen. It works for most meteorites, but this one was weird because we found some compact fragments that wouldn't break apart.
The researchers looked deeper to find out why they were so strong. The scientists were able to see the chondrules using computed tomography. The chondrules were all in the same direction in the Aguas Zarcas fragments. This was a sign that the fragments had been hit.
The meteorite's story was told by the pictures of Bennu's popcorning surface. Early in the solar system's history, Bennu and Aguas Zarcas formed. It's possible that the fragment that hit Earth was similar to the one that hit Bennu.
The researchers concluded that the parent asteroid of Aguas Zarcas had a high-speed collision. The rock broke apart due to the dramatic temperature changes that occur when an asteroid rotates. The side facing away from the sun is hotter than the side facing away.
There is a difference between asteroids, comets and meteorites.
This gravel is thrown away from the asteroid surface. It's not clear if another collision is necessary or if the same thermal stress can be used. The pebbles slow down the asteroid. The pebbles fall onto parts of the surface that never underwent an impact as a result of the main asteroid body's pulling. The asteroid went through another collision that made the unimpacted fragments into a single rock.
Everything was packed together. The fragment that reached Earth may have been broken off by this.
Scientists have learned from observations of Bennu that asteroids spit off pebbles. The low-level events are more important for the asteroid's composition.
This would be expected in other meteorites. People have yet to look for it.
It was originally published on Live Science
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