Matrix Mineralogy of the Least Altered CM-Related Chondrite Asuka 12169

T. Noguchi, M. Yasutake, A. Tsuchiyama, A. Miyake, M. Kimura, A. Yamaguchi, N. Imae, K. Uesugi, A. Takeuchi

51st Lunar and Planetary Science Conference (2020), Abstract #1666


“Almost all CM chondrites experienced varying degrees of interaction between anhydrous phases and liquid water (aqueous alteration) and thermal metamorphism [1, 2]. Reflectance spectra of the asteroid Ryugu that has been explored by Hayabusa 2 spacecraft suggest that the surface of Ryugu experienced partial dehydration due to thermal metamorphism and/or shock heating [3, 4]. It is also pointed out that Ryugu may consist of carbon-rich, partially hydrated, possibly comet-like material [4]. In addition, it is worthwhile to examine the possibility if the surface material experienced weak aqueous alteration. Therefore, it is important to understand CM chondrites that experienced an early stage of aqueous alteration. Just a few such meteorites fall into such category: Paris and Yamato 791198 [5-7]. Recently, it was pointed out that Asuka (A) 12169 experienced very low degree of thermal metamorphism and aqueous alteration [8]. Here we present our preliminary results on the mineralogy of matrix of this meteorite. “