Mineralogy and petrology of fine‐grained samples recovered from the asteroid (162173) Ryugu
T. Noguchi, Toru Matsumoto, Akira Miyake, Yohei Igami, Mitsutaka Haruta, Hikaru Saito, Satoshi Hata, Yusuke Seto, Masaaki Miyahara, Naotaka Tomioka, H. A. Ishii, J. P. Bradley, Kenta K. Ohtaki, E. Dobrică, Hugues Leroux, Corentin Le Guillou, Damien Jacob, Francisco de la Peña, Sylvain Laforet, Bahae‐Eddine Mouloud, Maya Marinova, F. Langenhorst, Dennis Harries, Pierre Beck, Van T. H. Phan, Rolando Rebois, N. M. Abreu, Jennifer Gray, T. J. Zega, Pierre-Marie Zanetta, M. S. Thompson, R. M. Stroud, Kate Burgess, Brittany A. Cymes, J. C. Bridges, L. J. Hicks, Martin Lee, Luke Daly, P. A. Bland, William A. Smith, S. McFadzean, Pierre‐Etienne Martin, Paul A.J. Bagot, Dennis Fougerouse, David W. Saxey, Steven M. Reddy, William D.A. Rickard, M. E. Zolensky, D. Frank, James Martinez, A. Tsuchiyama, Masahiro Yasutake, Junya Matsuno, Shota Okumura, Itaru Mitsukawa, Kentaro Uesugi, Masayuki Uesugi, Akihisa Takeuchi, Mingqi Sun, Satomi Enju, Aki Takigawa, Tatsuhiro Michikami, Tomoki Nakamura, Megumi Matsumoto, Yusuke Nakauchi, Masanao Abe, Satoru Nakazawa, Tatsuaki Okada, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Makoto Yoshikawa, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tomohiro Usui, Toru Yada, Hisayoshi Yurimoto, K. Nagashima, Noriyuki Kawasaki, Naoya Sakamotoa, P. Höppe, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Sei‐ichiro Watanabe, Yuichi Tsuda
Abstract
Abstract Samples returned from the carbonaceous asteroid (162173) Ryugu by the Hayabusa2 mission revealed that Ryugu is composed of materials consistent with CI chondrites and some types of space weathering. We report detailed mineralogy of the fine‐grained Ryugu samples allocated to our “Sand” team and report additional space weathering features found on the grains. The dominant mineralogy is composed of a fine‐grained mixture of Mg‐rich saponite and serpentine, magnetite, pyrrhotite, pentlandite, dolomite, and Fe‐bearing magnesite. These grains have mineralogy comparable to that of CI chondrites, showing severe aqueous alteration but lacking ferrihydrite and sulfate. These results are similar to previous works on large Ryugu grains. In addition to the major minerals, we also find many minerals that are rare or have not been reported among CI chondrites. Accessory minerals identified are hydroxyapatite, Mg‐Na phosphate, olivine, low‐Ca pyroxene, Mg‐Al spinel, chromite, manganochromite, eskolaite, ilmenite, cubanite, polydymite, transjordanite, schreibersite, calcite, moissanite, and poorly crystalline phyllosilicate. We also show scanning transmission electron microscope and scanning electron microscope compositional maps and images of some space‐weathered grains and severely heated and melted grains. Although our mineralogical results are consistent with that of millimeter‐sized grains, the fine‐grained fraction is best suited to investigate impact‐induced space weathering.