A dehydrated space-weathered skin cloaking the hydrated interior of Ryugu
Authors: Noguchi Takaaki , Matsumoto Toru , Miyake Akira , Igami Yohei , Haruta Mitsutaka , Saito Hikaru , Hata Satoshi , Seto Yusuke , Miyahara Masaaki , Tomioka Naotaka , Ishii Hope A. , Bradley John P. , Ohtaki Kenta K. , Dobrică Elena , Leroux Hugues , Le Guillou Corentin , Jacob Damien , de la Peña Francisco , Laforet Sylvain , Marinova Maya , Langenhorst Falko , Harries Dennis , Beck Pierre , Phan Thi H. V. , Rebois Rolando , Abreu Neyda M. , Gray Jennifer , Zega Thomas , Zanetta Pierre-M. , Thompson Michelle S. , Stroud Rhonda , Burgess Kate , Cymes Brittany A. , Bridges John C. , Hicks Leon , Lee Martin R. , Daly Luke , Bland Phil A. , Zolensky Michael E. , Frank David R. , Martinez James , Tsuchiyama Akira , Yasutake Masahiro , Matsuno Junya , Okumura Shota , Mitsukawa Itaru , Uesugi Kentaro , Uesugi Masayuki , Takeuchi Akihisa , Sun Mingqi , Enju Satomi , Takigawa Aki , Michikami Tatsuhiro , Nakamura Tomoki , Matsumoto Megumi , Nakauchi Yusuke , Abe Masanao , Arakawa Masahiko , Fujii Atsushi , Hayakawa Masahiko , Hirata Naru , Hirata Naoyuki , Honda Rie , Honda Chikatoshi , Hosoda Satoshi , Iijima Yu-ichi , Ikeda Hitoshi , Ishiguro Masateru , Ishihara Yoshiaki , Iwata Takahiro , Kawahara Kousuke , Kikuchi Shota , Kitazato Kohei , Matsumoto Koji , Matsuoka Moe , Mimasu Yuya , Miura Akira , Morota Tomokatsu , Nakazawa Satoru , Namiki Noriyuki , Noda Hirotomo , Noguchi Rina , Ogawa Naoko , Ogawa Kazunori , Okada Tatsuaki , Okamoto Chisato , Ono Go , Ozaki Masanobu , Saiki Takanao , Sakatani Naoya , Sawada Hirotaka , Senshu Hiroki , Shimaki Yuri , Shirai Kei , Sugita Seiji , Takei Yuto , Takeuchi Hiroshi , Tanaka Satoshi , Tatsumi Eri , Terui Fuyuto , Tsukizaki Ryudo , Wada Koji , Yamada Manabu , Yamada Tetsuya , Yamamoto Yukio , Yano Hajime , Yokota Yasuhiro , Yoshihara Keisuke , Yoshikawa Makoto , Yoshikawa Kent , Fukai Ryohta , Furuya Shizuho , Hatakeda Kentaro , Hayashi Tasuku , Hitomi Yuya , Kumagai Kazuya , Miyazaki Akiko , Nakato Aiko , Nishimura Masahiro , Soejima Hiromichi , Suzuki Ayako I. , Usui Tomohiro , Yada Toru , Yamamoto Daiki , Yogata Kasumi , Yoshitake Miwa , Connolly Harold C. , Lauretta Dante S. , Yurimoto Hisayoshi , Nagashima Kazuhide , Kawasaki Noriyuki , Sakamoto Naoya , Okazaki Ryuji , Yabuta Hikaru , Naraoka Hiroshi , Sakamoto Kanako , Tachibana Shogo , Watanabe Sei-ichiro , Tsuda Yuichi 
Published: December 2022

Without a protective atmosphere, space-exposed surfaces of airless Solar System bodies gradually experience an alteration in composition, structure and optical properties through a collective process called space weathering. The return of samples from near-Earth asteroid (162173) Ryugu by Hayabusa2 provides the first opportunity for laboratory study of space-weathering signatures on the most abundant type of inner solar system body: a C-type asteroid, composed of materials largely unchanged since the formation of the Solar System. Weathered Ryugu grains show areas of surface amorphization and partial melting of phyllosilicates, in which reduction from Fe3+ to Fe2+ and dehydration developed. Space weathering probably contributed to dehydration by dehydroxylation of Ryugu surface phyllosilicates that had already lost interlayer water molecules and to weakening of the 2.7 µm hydroxyl (–OH) band in reflectance spectra. For C-type asteroids in general, this indicates that a weak 2.7 µm band can signify space-weathering-induced surface dehydration, rather than bulk volatile loss.