After analyzing samples from the asteroid Ryugu, collected by the Hayabusa-2 mission, researchers from Tohoku University in Japan have found what appear to be the oldest solid compounds in the solar system ever used in studies. Analyzes of isotopes in the material indicate that asteroid grains have been transported to distant regions in our system.
The asteroid Ryugu is about 1 km across. It was visited in 2019 by the Japanese Hayabusa-2 mission, which touched its surface and fired a projectile that, upon encountering the asteroid, released debris. The procedure yielded more than 5 kg of samples, which reached Earth in December 2020.
For the analysis, the researchers worked with chondrules-like bodies (spherical mineral granules) with rich calcium and aluminum contents (or “CAIs,” in their English acronym). Grains are typical components of meteorites of the chondrite type, which come from the asteroid belt and reach Earth without suffering the effects of other processes.
They also analyzed the ratio of different isotopes of oxygen, that is, atoms of an element with changes in mass due to the difference in the number of neutrons in their nuclei. Added to studies of grain size and composition, isotopes found in the samples have shown that they likely have an ancient origin.
Studying the Ryugu samples is a way of examining “new” material, which was collected from an asteroid that was, at the time, about 15 million kilometers from Earth – and what’s even more curious here is that analyzes by other teams have suggested, in fact, that Ryugu was formed. Almost at the edge of the solar system, far from Earth.
However, the team found that the grains in the Ryugu samples were likely transported on tracks from the gradually expanding circles that began in the young inner solar system. Then, they moved to the outermost region and coalesced into the body and ended up fragmented, giving rise to the asteroid Ryugu.
Daisuke Nakashima, the geochemist who led the study, explains that they now want to analyze more solid compounds on the Ryugu asteroid to better understand the radial transport observed in the particles. “This is basic research into the ancient events that shaped our solar system.”
The article with the results of the study has been published in the journal Nature Communications.
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