[B-CG06] Rock-Bio Interactions and its Applications

[BCG06-06] A summary of the analytical work on Ryugu particles by Phase2 Kochi curation

★Invited Papers

*Motoo Ito¹, Naotaka Tomioka¹, Masayuki Uesugi², Akira Yamaguchi³, Naoki Shirai⁴, Takuji Ohigashi⁷, Ming-Chang Liu⁵, Richard Greenwood⁶, Makoto Kimura³, Naoya Imae³, Kentaro Uesugi², Aiko Nakato⁸, Kasumi Yogata⁸, Hayato Yuzawa⁹, Toru Yada⁸, Masanao Abe⁸, Tomohiro Usui⁸, Sei-ichiro WATANABE¹⁰, Yuichi Tsuda⁸, Phase2 Curation Kochi (1.JAMSTEC/Kochi Institute for Core Sample Research, 2.JASRI/SPring-8, 3.NIPR, 4.Kanagawa University, 5.LLNL, 6.Open University, 7.PF/KEK, 8.ISAS/JAXA, 9.UVSOR/IMS, 10.Nagoya University)

Keywords:C-type asteroid Ryugu, Extraterrestrial organics, phyllosilicate

Volatile and organic-rich C-type asteroids may have been one of the main sources of Earth’s water. Our best insight into their chemistry is currently provided by carbonaceous chondritic meteorites, but the meteorite record is biased: only the strongest types survive atmospheric entry and are then modified by interaction with the terrestrial environment. Here we present the results of a detailed bulk and microanalytical study of pristine Ryugu particles, brought to Earth by the Hayabusa2 spacecraft. Ryugu particles display a close compositional match with the chemically unfractionated, but aqueously altered, CI (Ivuna-type) chondrites, which are widely used as a proxy for the bulk Solar System composition. The sample shows an intricate spatial relationship between aliphatic-rich organics and phyllosilicates and indicates maximum temperatures of ~30°C during aqueous alteration. We find that heavy hydrogen and nitrogen abundances are consistent with an outer Solar System origin. Ryugu particles are the most uncontaminated and unfractionated extraterrestrial materials studied so far, and provide the best available match to the bulk Solar System composition.