Two of the photo voltaic system’s most well-known asteroids, Bennu and Ryugu, could also be fragments of a single large “parent” asteroid that was smashed to items billions of years in the past, new knowledge from the James Webb Space Telescope (JWST) reveals.
If true, the sibling house rocks — which have each lately been visited by spacecraft that efficiently returned samples of them to Earth — might make clear how asteroid households are created and dispersed all through our cosmic neighborhood.
Bennu is a roughly 1,650-foot-wide (500 meters) asteroid lately visited by NASA’s OSIRIS-REx mission, which touched down on the space rock in 2022 and collected samples that were returned to Earth in September 2023, and have since yielded several promising discoveries. Ryugu, meanwhile, spans around 2,950 feet (900 m) and was visited by Japan’s Hayabusa2 probe in 2019, which delivered samples of the asteroid to our planet in December 2020.
Both space rocks are shaped like spinning tops and are considered “potentially hazardous asteroids” due to their size and relative proximity to Earth. Neither poses a perceivable threat to our planet for at least the next century — although NASA is keeping a close eye on Bennu, due to the slim chance it could collide with us in 2182.
There are several different ideas about where the two asteroids originate from, but one leading theory is that the pair belongs to the Polana asteroid family, which was created when a massive asteroid broke apart in the early solar system. The largest remaining chunk of this ancient asteroid is 142 Polana, a gigantic space rock spanning more than 34 miles (55 kilometers) wide that is located in the main asteroid belt between Mars and Jupiter.
In a new study, published Aug. 18 in The Planetary Science Journal, researchers in contrast spectroscopy knowledge of 142 Polana, collected by JWST, with the samples of Bennu and Ryugu introduced again to Earth. The researchers discovered that every one three house rocks bear a placing resemblance to at least one one other, suggesting all of them originated from the identical guardian asteroid. However, it’s nonetheless not 100% sure if so.
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“Very early in the formation of the solar system, we believe large asteroids collided and broke into pieces to form an ‘asteroid family’ with Polana as the largest remaining body,” examine lead writer Anicia Arredondo, a planetary scientist at Southwest Research Institute (SwRI) in Texas, mentioned in a statement. The findings “suggest that remnants of that collision not only created Polana, but also Bennu and Ryugu as well,” she added.
All three asteroids share the identical core composition of components and minerals, comparable to carbon and magnetite, a uncommon type of iron oxide. However, there are some delicate variations within the concentrations of those substances between 142 Polana and the samples of Bennu and Ryugu, which means a particular conclusion can’t be reached but.
The examine crew believes that these discrepancies are seemingly attributable to the asteroids’ respective outer surfaces, which have every been barely altered since they broke aside.
“Bennu and Ryugu are now much closer to the sun than Polana, so their surfaces may be more affected by solar radiation and solar particles,” examine co-author Tracy Becker, a SwRI planetary scientist, mentioned within the assertion. “Likewise, Polana is possibly older than Bennu and Ryugu and thus would have been exposed to micrometeoroid impacts for a longer period,” she added. “That could also change aspects of its surface, including its composition.”
Despite the variations, the researchers say {that a} shared guardian asteroid is the very best rationalization for the house rocks’ origins.
“They are similar enough that we feel confident that all three asteroids could have come from the same parent body, ” Arredondo mentioned.