Spectrally blue hydrated parent body of asteroid (162173) Ryugu

Ryugu is a carbonaceous rubble-pile asteroid visited by the Hayabusa2 spacecraft. Hayabusa2 remote-sensing observations find that both north and south pole regions preserve spectrally blue carbonaceous chondritic material with a 0–3% deep 0.7-µm band absorption, indicative of Fe-bearing phyllosilicates. This study reports that Ryugu's parent body experienced intensive aqueous alteration and subsequent thermal metamorphism at 570–670 K (300–400 °C), suggesting heating by radioactive decay of short-lived radionuclides possibly due to early formation 2–2.5 Ma. Samples returned to Earth by Hayabusa2 will provide insights into this solar system epoch.

Eri Tatsumi, Naoya Sakatani, Lucie Riu, Moe Matsuoka, Rie Honda, Tomokatsu Morota, Shingo Kameda, Tomoki Nakamura, Michael Zolensky, Rosario Brunetto, Takahiro Hiroi, Sho Sasaki, Sei'ichiro Watanabe, Satoshi Tanaka, Jun Takita, Cédric Pilorget, Julia de León, Marcel Popescu, Juan Luis Rizos, Javier Licandro, Ernesto Palomba, Deborah Domingue, Faith Vilas, Humberto Campins, Yuichiro Cho, Kazuo Yoshioka, Hidehiko Suzuki, Chikatoshi Honda, Kazunori Ogawa, Kohei Kitazato, Naru Hirata, Naoyuki Hirata, Yuichi Tsuda, Makoto Yoshikawa, Takanao Saiki, Fuyuto Terui, Satoru Nakazawa, Yuto Takei, Hiroshi Takeuchi, Yukio Yamamoto, Tatsuaki Okada, Yuri Shimaki, Kei Shirai, Seiji Sugita