2026-09-11 北海道大学,茨城大学,茨城大学,海洋研究開発機構,東京科学大学,東京大学
＜関連情報＞
- https://www.hokudai.ac.jp/news/2026/09/4565.html
- https://www.science.org/doi/10.1126/science.adw4498
小惑星リュウグウとイヴナ型隕石の母天体は他の炭素質隕石の母天体よりも前に形成された The parent bodies of Ryugu and Ivuna formed before those of other carbonaceous chondrites
Noriyuki Kawasaki, Kazuhide Nagashima, Naoya Sakamoto, Wataru Fujiya, […] , and Hisayoshi Yurimoto
Science Published:10 Sep 2026
DOI:https://doi.org/10.1126/science.adw4498
Abstract
Most carbonaceous chondrite (CC) meteorites contain abundant chondrules, millimeter-scale spherical inclusions of previously molten material. Ivuna-type carbonaceous chondrites (CIs) do not contain chondrules, nor do samples of the carbonaceous asteroid Ryugu. CIs and Ryugu share isotopic properties distinct from those of other CCs, implying that their parent bodies formed at a different time or place than those of other CCs. We applied manganese-chromium dating and oxygen isotope thermometry to Ryugu and Ivuna samples. The results indicate that the parent bodies of Ryugu and Ivuna formed less than 2 million years after the beginning of Solar System formation—before the majority of chondrules in CCs and the parent bodies of other CCs formed. This implies that Ryugu and CIs are remnants of an earlier generation of carbonaceous planetesimals.
