Jens Barosch, Larry R. Nittler, Jianhua Wang, Conel M. O'D. Alexander, Bradley T. De Gregorio, Cécile Engrand, Yoko Kebukawa, Kazuhide Nagashima, Rhonda M. Stroud, Hikaru Yabuta, Yoshinari Abe, Jérôme Aléon, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Laure Bejach, Martin Bizzarro, Lydie Bonal, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, George D. Cody, Emmanuel Dartois, Nicolas Dauphas, Andrew M. Davis, Alexandre Dazzi, Ariane Deniset-Besseau, Tommaso Di Rocco, Jean Duprat, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Minako Hashiguchi, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Motoo Ito, Shoichi Itoh, Kanami Kamide, Noriyuki Kawasaki, A. L. David Kilcoyne, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Mutsumi Komatsu, Alexander N. Krot, Ming-Chang Liu, Zita Martins, Yuki Masuda, Jérémie Mathurin, Kevin D. McKeegan, Gilles Montagnac, Mayu Morita, Smail Mostefaoui, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Ann N. Nguyen, Takuji Ohigashi, Taiga Okumura, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Eric Quirico, Laurent Remusat, Sara S. Russell, Naoya Sakamoto, Scott A. Sandford, Maria Schönbächler, Miho Shigenaka, Hiroki Suga, Lauren Tafla, Yoshio Takahashi, Yasuo Takeichi, Yusuke Tamenori, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Maximilien Verdier-Paoletti, Sohei Wada, Meenakshi Wadhwa, Daisuke Wakabayashi, Richard J. Walker, Katsuyuki Yamashita, Shohei Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Satoru Nakazawa, Masahiro Nishimura, Tatsuaki Okada, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Toru Yada, Kasumi Yogata, Makoto Yoshikawa, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Shogo Tachibana, Hisayoshi Yurimoto
ASTROPHYSICAL JOURNAL LETTERS 935(1) 2022年8月16日
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$^{+4.7}_{-2.6}$ ppm for O-anomalous grains, 25$^{+6}_{-5}$ ppm
for SiC grains and 11$^{+5}_{-3}$ 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 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 $^{+7}_{-6}$ ppm SiC and 9.0$^{+5.3}_{-4.6}$ 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.