R5: Extraterrestrial materials

[R5-07] Petrology and mineralogy of olivine in asteroidal Ryugu samples

*Takashi Mikouchi¹, Hideto Yoshida², Tomoki Nakamura³, Michael E. Zolesnky⁴, Daisuke Nakashima³, Kenji Hagiya⁵, Mizuha Kikuiri³, Tomoyo Morita³, Kana Amano³, Eiichi Kagawa², Hisayoshi Yurimoto⁶, Takaaki Noguchi⁷, Ryuji Okazaki⁸, Hikaru Yabuta⁹, Hiroshi Naraoka⁸ (1. Univ. Tokyo, 2. Univ. Tokyo, 3. Tohoku Univ., 4. NASA JSC, 5. Univ. Hyogo, 6. Hokkaido Univ., 7. Kyoto Univ., 8. Kyushu Univ., 9. Hiroshima Univ.)

Keywords:Asteroid Ryugu, Olivine, CI chondrite, FE-EPMA, Hayabusa2 spacecraft

The asteroid Ryugu sample returned by the JAXA Hayabusa2 spacecraft consists mainly of phyllosilicates, but a small amount of olivine (Fo~99), which is thought to have escaped aqueous alteration, is present. CI chondrites (Orugeil and Ivuna) analyzed as a comparison also had olivine texture (texture and size) and mineral compositions identical to those of the Ryugu sample. The absence of olivine in the Room A sample suggests that the two touchdowns yielded samples with different characteristics.