Presolar Stardust in Asteroid Ryugu
Authors: Barosch Jens , Nittler Larry R. , Wang Jianhua , O’D. Alexander Conel M. , De Gregorio Bradley T. , Engrand Cécile , Kebukawa Yoko , Nagashima Kazuhide , Stroud Rhonda M. , Yabuta Hikaru , Abe Yoshinari , Aléon Jérôme , Amari Sachiko , Amelin Yuri , Bajo Ken-ichi , Bejach Laure , Bizzarro Martin , Bonal Lydie , Bouvier Audrey , Carlson Richard W. , Chaussidon Marc , Choi Byeon-Gak , Cody George D. , Dartois Emmanuel , Dauphas Nicolas , Davis Andrew M. , Dazzi Alexandre , Deniset-Besseau Ariane , Di Rocco Tommaso , Duprat Jean , Fujiya Wataru , Fukai Ryota , Gautam Ikshu , Haba Makiko K. , Hashiguchi Minako , Hibiya Yuki , Hidaka Hiroshi , Homma Hisashi , Hoppe Peter , Huss Gary R. , Ichida Kiyohiro , Iizuka Tsuyoshi , Ireland Trevor R. , Ishikawa Akira , Ito Motoo , Itoh Shoichi , Kamide Kanami , Kawasaki Noriyuki , David Kilcoyne A. L. , Kita Noriko T. , Kitajima Kouki , Kleine Thorsten , Komatani Shintaro , Komatsu Mutsumi , Krot Alexander N. , Liu Ming-Chang , Martins Zita , Masuda Yuki , Mathurin Jérémie , McKeegan Kevin D. , Montagnac Gilles , Morita Mayu , Mostefaoui Smail , Motomura Kazuko , Moynier Frédéric , Nakai Izumi , Nguyen Ann N. , Ohigashi Takuji , Okumura Taiga , Onose Morihiko , Pack Andreas , Park Changkun , Piani Laurette , Qin Liping , Quirico Eric , Remusat Laurent , Russell Sara S. , Sakamoto Naoya , Sandford Scott A. , Schönbächler Maria , Shigenaka Miho , Suga Hiroki , Tafla Lauren , Takahashi Yoshio , Takeichi Yasuo , Tamenori Yusuke , Tang Haolan , Terada Kentaro , Terada Yasuko , Usui Tomohiro , Verdier-Paoletti Maximilien , Wada Sohei , Wadhwa Meenakshi , Wakabayashi Daisuke , Walker Richard J. , Yamashita Katsuyuki , Yamashita Shohei , Yin Qing-Zhu , Yokoyama Tetsuya , Yoneda Shigekazu , Young Edward D. , Yui Hiroharu , Zhang Ai-Cheng , Abe Masanao , Miyazaki Akiko , Nakato Aiko , Nakazawa Satoru , Nishimura Masahiro , Okada Tatsuaki , Saiki Takanao , Tanaka Satoshi , Terui Fuyuto , Tsuda Yuichi , Watanabe Sei-ichiro , Yada Toru , Yogata Kasumi , Yoshikawa Makoto , Nakamura Tomoki , Naraoka Hiroshi , Noguchi Takaaki , Okazaki Ryuji , Sakamoto Kanako , Tachibana Shogo , Yurimoto Hisayoshi 
Published: August 2022

Abstract
We have conducted a NanoSIMS-based search for presolar material in samples recently returned from C-type asteroid Ryugu as part of JAXA's Hayabusa2 mission. We report the detection of all major presolar grain types with O- and C-anomalous isotopic compositions typically identified in carbonaceous chondrite meteorites: 1 silicate, 1 oxide, 1 O-anomalous supernova grain of ambiguous phase, 38 SiC, and 16 carbonaceous grains. At least two of the carbonaceous grains are presolar graphites, whereas several grains with moderate C isotopic anomalies are probably organics. The presolar silicate was located in a clast with a less altered lithology than the typical extensively aqueously altered Ryugu matrix. The matrix-normalized presolar grain abundances in Ryugu are

4.8

−
2.6

+
4.7

ppm for O-anomalous grains,

25

−
5

+
6

ppm for SiC grains, and

11

−
3

+
5

ppm for carbonaceous grains. Ryugu is isotopically and petrologically similar to carbonaceous Ivuna-type (CI) chondrites. To compare the in situ presolar grain abundances of Ryugu with CI chondrites, we also mapped Ivuna and Orgueil samples and found a total of 15 SiC grains and 6 carbonaceous grains. No O-anomalous grains were detected. The matrix-normalized presolar grain abundances in the CI chondrites are similar to those in Ryugu:

23

−
6

+
7

ppm SiC and

9.0

−
3.6

+
5.4

ppm carbonaceous grains. Thus, our results provide further evidence in support of the Ryugu–CI connection. They also reveal intriguing hints of small-scale heterogeneities in the Ryugu samples, such as locally distinct degrees of alteration that allowed the preservation of delicate presolar material.