近日，日本北海道大学Noriyuki Kawasaki团队报道了龙宫和伊武纳的母体形成于其他碳质球粒陨石的母体之前。
大多数碳质球粒陨石（CC）含有丰富的球粒，即毫米级、由曾经熔融物质形成的球形包体。伊武纳型碳质球粒陨石（CIs）不含球粒，碳质小行星龙宫的样品也不含球粒。CI型陨石与龙宫具有不同于其他CC的同位素特征，暗示它们的母体形成时间或地点与其他CC的母体不同。
研究组对龙宫和伊武纳样品应用了锰-铬定年和氧同位素测温。结果表明，龙宫和伊武纳的母体形成于太阳系形成开始后不到200万年——早于CC中大多数球粒以及其他CC母体形成。这意味着龙宫和CI型陨石是更早一代碳质星子的残余。
附：英文原文
Title: The parent bodies of Ryugu and Ivuna formed before those of other carbonaceous chondrites
Author: Noriyuki Kawasaki, Kazuhide Nagashima, Naoya Sakamoto, Wataru Fujiya, Sota Arakawa, Ken-ichi Bajo, Noriko T. Kita, Kouki Kitajima, Alexander N. Krot, Gary R. Huss, Yoshinari Abe, Jérme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Thorsten Kleine, Shintaro Komatani, Ming-Chang Liu, Yuki Masuda, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Ann Nguyen, Larry Nittler, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Maria Schnbchler, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
Issue&Volume: 2026-09-10
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.
DOI: 10.1126/science.adw4498
Source: https://www.science.org/doi/10.1126/science.adw4498