Collisional history of C-type asteroids revealed by in-situ U-Pb dating and micro-XRD measurements

Abstract

Both the existence of asteroid families such as Polana/Eulalia and the rubble pile structures of 162173 Ryugu and 101955 Bennu are absolute evidence that large parent bodies of C-type asteroids (>100 km in diameter) have been disrupted into smaller pieces by catastrophic collisions. However, unlike ordinary meteorites related to S-type asteroids, the impact history of carbonaceous chondrites has not been well understood (Amsellen et al. 2020). In this study, we investigated the U-Pb systematics of apatites in four carbonaceous chondrites (B-7904, Y-86695, Y-82054 and Y-82098) with traces of thermal metamorphism using the NanoSIMS 50 to obtain information on crystallization age and secondary thermal alteration age. Furthermore, we estimated the pressure experienced by the samples based on micro-X-ray diffraction measurements for minerals in the meteorites. At the conference, we will discuss the obtained ages and the description of impact metamorphism experienced by these samples.＜References＞Amsellem E. et al. (2020) Icarus 339, 113593.