日本北海道大学教授Hisayoshi Yurimoto等研究员及其课题组的最新研究探明无水原生矿物的氧同位素能显示小行星Ryugu和彗星81P/Wild2之间的亲缘关系。相关论文于2022年12月16日发表于国际顶尖学术期刊《科学-进展》杂志上。

该研究团队发现，Ryugu和CI球粒陨石中的高温无水原生矿物氧同位素组成呈现双峰分布:富¹⁶O(与耐火包体有关)和贫¹⁶O(与球粒有关)。富含¹⁶O和缺乏¹⁶O的矿物可能都是在太阳原行星盘内部形成的，随后被向外输送。Ryugu和CI球粒陨石中富¹⁶O和贫¹⁶O的矿物的丰度比高于其他碳质球粒陨石群，但与81P/Wild2彗星相似，表明Ryugu和CI球粒陨石是在太阳系外靠近彗星吸积区吸积的。

据悉，从小行星(162173)Ryugu返回的地外物质主要由低温水形成的次生矿物组成，在化学和矿物学上与CI (ivuna型)碳质球粒陨石相似。

附：英文原文

Title: Oxygen isotopes of anhydrous primary minerals show kinship between asteroid Ryugu and comet 81P/Wild2

Author: Noriyuki Kawasaki, Kazuhide Nagashima, Naoya Sakamoto, Toru Matsumoto, Ken-ichi Bajo, Sohei Wada, Yohei Igami, Akira Miyake, Takaaki Noguchi, Daiki Yamamoto, Sara S. Russell, 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, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Motoo Ito, Shoichi Itoh, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Maria Schnbchler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, 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, 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: 2022-12-16

Abstract: The extraterrestrial materials returned from asteroid (162173) Ryugu consist predominantly of low-temperature aqueously formed secondary minerals and are chemically and mineralogically similar to CI (Ivuna-type) carbonaceous chondrites. Here, we show that high-temperature anhydrous primary minerals in Ryugu and CI chondrites exhibit a bimodal distribution of oxygen isotopic compositions: ¹⁶O-rich (associated with refractory inclusions) and ¹⁶O-poor (associated with chondrules). Both the ¹⁶O-rich and ¹⁶O-poor minerals probably formed in the inner solar protoplanetary disk and were subsequently transported outward. The abundance ratios of the ¹⁶O-rich to ¹⁶O-poor minerals in Ryugu and CI chondrites are higher than in other carbonaceous chondrite groups but are similar to that of comet 81P/Wild2, suggesting that Ryugu and CI chondrites accreted in the outer Solar System closer to the accretion region of comets.

DOI: ade2067

Source: https://www.science.org/doi/10.1126/sciadv.ade2067