Asteroid sample suggests more complex early solar system chemistry
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In December 2020, the Hyabusa 2 mission returned samples from the near-Earth asteroid Ryugu.
Since then, scientists around the world have been analyzing what’s essentially a rocky record of our solar system’s infancy.
A new paper in the journal Science Advances supports the hypothesis that the early solar system was more chemically diverse than once thought.
“The fundamental exciting thing about this result is that it's telling us something about what kinds of dynamics might have existed in the earliest history of our solar system that could have created chemically and isotopically distinct reservoirs,” said co-author Meenakshi Wadhwa, director of ASU’s School of Earth and Space Exploration.
Asteroids like Ryugu hold an isotopic fingerprint — a ratio of different versions of elements, such as iron, with differing numbers of neutrons.
This mix of elemental “flavors” uniquely reflects the neighborhood in which such bodies formed, and they retain the signature even if they’re moved around by gravity or broken apart and reassembled.
Previous work suggested two such regions in the primordial solar system, divided during the formation of an infant Jupiter.
“Those reservoirs separate because, when you start forming some of these giant planets, you basically are creating a gap in the disk,” said Wadhwa.
The new data provides evidence of a third geochemical neighborhood.
“The third reservoir might have been very much further out than even Jupiter — so, somewhere near where the ice giants formed, near Neptune and Uranus,” she said.
Ryugu’s isotopic signature reveals that it shares a lot in common with a subgroup of carbon-rich meteorites called Ivuna-type carbonaceous chondrites. That could mean they were once part of the same parent body, but scientists cannot yet say that with certainty.
The asteroid’s later inward migration around 5 million years ago gave today’s scientists a unique chance to study an object from the hard-to-reach outer solar system.
“We are sampling materials in these near-Earth asteroids like Ryugu that likely originally formed in places that are otherwise very hard to reach with spacecraft,” said Wadhwa.
