[B-CG06] 岩石生命相互作用とその応用

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

★Invited Papers

*伊藤 元雄¹、富岡 尚敬¹、上椙 真之²、山口 亮³、白井 直樹⁴、大東 琢治⁷、Liu Ming-Chang⁵、Greenwood Richard⁶、木村 眞³、今栄 直也³、上杉 健太朗²、中藤 亜衣子⁸、与賀田 佳澄⁸、湯沢 勇人⁹、矢田 達⁸、安部 正真⁸、臼井 寛裕⁸、渡邊 誠一郎¹⁰、津田 雄一⁸、Phase2 Curation 高知 (1.海洋研究開発機構・高知コア研究所、2.公益財団法人高輝度光科学研究センター、3.国立極地研究所、4.神奈川大学、5.ローレンス・リバモア国立研究所、6.オープン大学、7.高エネルギー加速器研究機構・フォトンファクトリー、8.宇宙航空研究開発機構・宇宙科学研究所、9.分子科学研究所・UVSOR、10.名古屋大学)

キーワード：小惑星リュウグウ、地球外有機物、フィロシリケイト

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.