Researchers from Japanese institutions have completed a detailed analysis of the grains collected from the asteroid Ryugu, a finding reported by Tohoku University. Ryugu is a near-Earth object measuring about 900 meters across, renowned for its 2019 encounter with the Japanese spacecraft Hayabusa-2, which retrieved surface material and brought it back to Earth. The returned samples have proven to be an invaluable archive of information about how asteroids are formed and structured, offering a direct glimpse into the early solar system.
The latest examination centers on rock fragments that are rich in calcium and aluminum, particularly elements and inclusions known as CAIs. These inclusions are notable because some asteroids from the Main Belt that occasionally intersect Earth’s vicinity also contain CAIs. The new study builds on decades of research suggesting that Ryugu, now nearer to our planet, likely originated in the outer regions of the solar system. The principal conclusion drawn from the isotopic analysis, which reveals solar proximity, along with microscopic examinations of grain structure, points to a more nuanced origin story: the CAI-bearing material may have formed in the inner solar system at the dawn of the solar system’s history and gradually migrated outward before Ryugu moved toward Earth.
According to the authors, CAIs and related materials appear to have formed a distinct body in the outer solar system during the early dispersal of materials that eventually coalesced into Ryugu. The study suggests that Ryugu’s journey involved an inward and outward redistribution of solid materials across the solar nebula, a process that likely left a lasting imprint on its composition. The researchers emphasize the importance of continuing to study these primordial solids to shed light on the mechanisms that transported material from the inner to the outer parts of the early solar system and to understand how such processes shaped the asteroid Ryugu before its Earth-bound encounter.
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