In 2020, the Japan Aerospace Exploration Company’s (JAXA) Hayabusa2 spacecraft accomplished its main mission when it returned samples of asteroid Ryugu to Earth. In 2023, NASA’s OSIRIS-REx additionally accomplished its main mission by returning samples of asteroid Bennu to Earth. Scientists in labs world wide have been learning these samples and have uncovered some surprises.
The Ryugu pattern contained uracil, one of many 4 RNA nucleotides which might be important for all times as we perceive it. That discovery signifies that asteroids might’ve performed a task in delivering the uncooked supplies for all times to Earth. The Bennu pattern contained its personal shock. It contained sudden phosphate compounds, which urged that it might be a splinter from a small, historic physique with an ocean.
These findings present how complicated asteroids will be, and that they are extra than simply chunks of house rock.
Asteroids are the fragments from collisions involving planetesimals. Every one is a puzzle piece that may assist astronomers uncover our Photo voltaic System’s historical past. One of many key endeavours in asteroid and Photo voltaic System science is figuring out which asteroids shared the identical guardian our bodies, which will help illuminate the general historical past of the Photo voltaic System.
New analysis in The Planetary Science Journal reveals that Bennu and Ryugu got here from the identical guardian physique. The analysis is “JWST Spectroscopy of (142) Polana: Connection to NEAs (101955) Bennu and (162173) Ryugu,” and the lead writer is Dr. Anicia Arredondo from the Southwest Analysis Institute.
Each are from the Polana collisional household in the primary asteroid belt (MAB) between Mars and Jupiter. It took greater than laboratory research of the samples to verify it. The JWST performed an necessary position, too, by acquiring each mid-infrared and near-infrared spectra from each asteroids.
“We current JWST Close to Infrared Spectrograph and Mid-Infrared Instrument spectroscopy of the guardian physique of the household, (142) Polana, and examine it with spacecraft and laboratory information of each near-Earth asteroids,” the authors write. “Spectral options at comparable wavelengths within the spectra of Polana and people of Bennu and Ryugu help the speculation that each asteroids originated within the Polana household.”
This determine reveals the hydrogen content material of asteroids decided by varied methods in different analysis. The Polana outcomes are added from this research. Shaded areas present the vary of H wt % for carbonaceous chondrites. Polana is just like Bennu and Ryugu and in contrast to the CI and CM chondrites. Picture Credit score: Arredondo et al. 2025. PSJ.
“Very early within the formation of the photo voltaic system, we imagine giant asteroids collided and broke into items to kind an ‘asteroid household’ with Polana as the most important remaining physique,” mentioned lead writer Arredondo in a press release. “Theories counsel that remnants of that collision not solely created Polana, but additionally Bennu and Ryugu as properly. To check that concept, we began taking a look at spectra of all three our bodies and evaluating them to 1 one other.”
“They’re comparable sufficient that we really feel assured that every one three asteroids might have come from the identical guardian physique,” Arredondo mentioned.
Polana is way bigger than each Ryugu and Bennu, at about 55 km in diameter. Bennu is barely about 500 meters in diameter, and Ryugu is barely about 850 meters in diameter. Polana could be very darkish, with an albedo of solely 0.045, and is a Kind F carbonaceous asteroid, a sub-group of the extra widespread C-type asteroid.
The researchers assume that after the collision that spawned them, Ryugu and Bennu have been pushed out of their orbits near Polana by Jupiter’s immense gravity. Consequently, the 2 smaller asteroids have been altered by their nearer proximity to the Solar.
“Polana, Bennu and Ryugu have all had their very own journeys via our photo voltaic system for the reason that impression that will have shaped them,” mentioned SwRI’s Dr. Tracy Becker, a co-author of the paper. “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.
There are some variations between the three, particularly across the depth and width of the two.7 μm function. This function signifies hydrated minerals, or water-bearing minerals, and tells scientists one thing about an asteroid’s historical past of thermal and aqueous alteration. “The variations within the depth and width of the two.7 μm function are extra outstanding between Polana and Ryugu than between Polana and Bennu. The reason for this distinction is unsure however might probably be on account of location within the early planetesimal or the results of house weathering,” the researchers write.
This determine compares NIRSpec Polana information to Bennu and Ryugu information. There are variations across the 2.7 micrometer function which might be probably on account of house weathering. Picture Credit score: Arredondo et al. 2025. PSJ.
“Likewise, Polana is probably older than Bennu and Ryugu and thus would have been uncovered to micrometeoroid impacts for an extended interval,” Becker added. “That would additionally change elements of its floor, together with its composition.”
The variations might additionally stem from variations within the guardian physique.
“The variations in hydration between Bennu and Ryugu don’t essentially imply that they arrive from completely different guardian our bodies,” the authors clarify. “Variations between the equally sized Bennu and Ryugu might be on account of guardian physique partial dehydration on account of inside heating. If Bennu got here from floor materials and Ryugu got here from interior materials, the guardian physique impression would produce completely different layers of compaction, which might trigger them to have completely different macroporosities and ranges of hydration.”
Of their conclusion, the authors state that regardless of variations, they’re assured that every one three our bodies share the identical guardian physique. “We discover that similarities within the shapes and strengths of most of the spectral options throughout the NIR and MIR, together with the outstanding OH function at 2.72 μm, help the speculation that Bennu and Ryugu might have originated within the new Polana household,” they write.
Some areas of the spectra require additional research to know and clarify, in response to the authors.
“The evaluation of the returned samples from each Bennu and Ryugu is ongoing, and future developments within the understanding of how floor processes manifest in NIR and MIR spectra will give extra insights into the interpretation of our Polana spectrum,” they conclude.
