Two of the photo voltaic system’s most well-known asteroids, Bennu and Ryugu, could also be fragments of a single large “guardian” asteroid that was smashed to items billions of years in the past, new knowledge from the James Webb House Telescope (JWST) reveals.
If true, the sibling area rocks — which have each just lately been visited by spacecraft that efficiently returned samples of them to Earth — may 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 just lately visited by NASA’s OSIRIS-REx mission, which touched down on the area rock in 2022 and picked up samples that had been returned to Earth in September 2023, and have since yielded a number of promising discoveries. Ryugu, in the meantime, spans round 2,950 toes (900 m) and was visited by Japan’s Hayabusa2 probe in 2019, which delivered samples of the asteroid to our planet in December 2020.
Each area rocks are formed like spinning tops and are thought of “doubtlessly hazardous asteroids” attributable to their dimension and relative proximity to Earth. Neither poses a perceivable menace to our planet for at the very least the subsequent century — though NASA is maintaining an in depth eye on Bennu, because of the slim likelihood it may collide with us in 2182.
There are a number of completely different concepts about the place the 2 asteroids originate from, however one main principle is that the pair belongs to the Polana asteroid household, which was created when a large asteroid broke aside within the early photo voltaic system. The biggest remaining chunk of this historic asteroid is 142 Polana, a huge area rock spanning greater than 34 miles (55 kilometers) broad that’s positioned in the primary asteroid belt between Mars and Jupiter.
In a brand new research, printed 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 area rocks bear a putting resemblance to at least one one other, suggesting all of them originated from the identical guardian asteroid. Nonetheless, it’s nonetheless not 100% sure if so.
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“Very early within the formation of the photo voltaic system, we imagine massive asteroids collided and broke into items to type an ‘asteroid household’ with Polana as the biggest remaining physique,” research lead creator Anicia Arredondo, a planetary scientist at Southwest Analysis Institute (SwRI) in Texas, stated in a assertion. The findings “counsel that remnants of that collision not solely created Polana, but in addition Bennu and Ryugu as effectively,” she added.
All three asteroids share the identical core composition of parts and minerals, similar to carbon and magnetite, a uncommon type of iron oxide. Nonetheless, there are some refined variations within the concentrations of those substances between 142 Polana and the samples of Bennu and Ryugu, that means a particular conclusion can’t be reached but.
The research staff believes that these discrepancies are possible attributable to the asteroids’ respective outer surfaces, which have every been barely altered since they broke aside.
“Bennu and Ryugu are actually a lot nearer to the solar than Polana, so their surfaces could also be extra affected by photo voltaic radiation and photo voltaic particles,” research co-author Tracy Becker, a SwRI planetary scientist, stated within the assertion. “Likewise, Polana is probably older than Bennu and Ryugu and thus would have been uncovered to micrometeoroid impacts for an extended interval,” she added. “That might additionally change features of its floor, together with its composition.”
Regardless of the variations, the researchers say {that a} shared guardian asteroid is the absolute best rationalization for the area rocks’ origins.
“They’re comparable sufficient that we really feel assured that every one three asteroids may have come from the identical guardian physique, ” Arredondo stated.
