Abundant presolar grains and primordial organics preserved in carbon-rich exogenous clasts in asteroid Ryugu
A. N. Nguyen, P. Mane, L. P. Keller, Laurette Piani, Yoshinari Abe, J. Aléon, C. M. O'd. Alexander, S. Amari, Yuri Amelin, Ken‐ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon‐Gak Choi, Nicolas Dauphas, A. M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, P. Höppe, G. R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, T. R. Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, N. T. Kita, Kouki Kitajima, T. Kleine, Shintaro Komatani, Alexander N. Krot, Ming‐Chang Liu, Yuki Masuda, K. D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, K. Nagashima, David Nesvorný, L. R. Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Liping Qin, S. S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, M. Wadhwa, R. J. Walker, Katsuyuki Yamashita, Qing‐Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward Young, Hiroharu Yui, Ai‐Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, T. 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
Abstract
Preliminary analyses of asteroid Ryugu samples show kinship to aqueously altered CI (Ivuna-type) chondrites, suggesting similar origins. We report identification of C-rich, particularly primitive clasts in Ryugu samples that contain preserved presolar silicate grains and exceptional abundances of presolar SiC and isotopically anomalous organic matter. The high presolar silicate abundance (104 ppm) indicates that the clast escaped extensive alteration. The 5 to 10 times higher abundances of presolar SiC (~235 ppm), N-rich organic matter, organics with N isotopic anomalies (1.2%), and organics with C isotopic anomalies (0.2%) in the primitive clasts compared to bulk Ryugu suggest that the clasts formed in a unique part of the protoplanetary disk enriched in presolar materials. These clasts likely represent previously unsampled outer solar system material that accreted onto Ryugu after aqueous alteration ceased, consistent with Ryugu's rubble pile origin.