NASA spacecraft discovers chunks of asteroid Vesta on asteroid Bennu

Osiris-Rex snapped these views of bright boulders on asteroid Bennu in 2019. They appear to have come from asteroid Vesta.

NASA/Goddard/University of Arizona

Asteroid Bennu, the subject of NASA’s Osiris-Rex mission, appears to be hosting some unusual souvenirs. In a case of cosmic CSI, researchers have traced the origin of some bright boulders on Bennu’s surface to a different asteroid named Vesta.

Osiris-Rex is currently in residence at Bennu, preparing for a daring sample collection operation in October. The spacecraft has already sent back a wealth of images and data from the “rubble pile” asteroid that was formed from fragments of a brutal collision.

The boulders in question range in size from 5 to 14 feet (about 1.5 to 4.3 meters) and look noticeably different than the darker surrounding material. 

A closer investigation of the odd rocks revealed signs of the mineral pyroxene, which is found on Vesta. After ruling out other possible ways pyroxene forms, the team was left with Vesta as the likely culprit. This was like tracing fingerprints discovered at a crime scene.  

“Our leading hypothesis is that Bennu inherited this material from its parent asteroid after a vestoid (a fragment from Vesta) struck the parent,” said NASA’s Hannah Kaplan in a statement on Monday. “Then, when the parent asteroid was catastrophically disrupted, a portion of its debris accumulated under its own gravity into Bennu, including some of the pyroxene from Vesta.”  

A NASA video gives a cute animated version of the research, which was published as a study in the journal Nature Astronomy on Monday.

“Observations reveal it’s not unusual for an asteroid to have material from another asteroid splashed across its surface,” NASA said.

Vesta is a notable asteroid that was visited by NASA’s Dawn mission in 2011 in the main asteroid belt between the orbits of Mars and Jupiter. Both Bennu and Vesta are ancient relics from the early solar system. 

Osiris-Rex’s sample return, if it goes well, could tell us a lot more about these enigmatic objects and their origins. NASA researchers are hoping a little taste of Vesta comes back to Earth along with bits of Bennu.

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