Mineralogical study of the Almahata Sitta ureilite

Abstract

We performed a mineralogical study of Almahata Sitta which was the first recovered asteroid fall (2008TC3) in history and found that it was composed of both coarse-grained and fine-grained lithic clasts of ureilites. The olivine and pyroxene mineralogy gave the cooling rate of 0.2-5 oC/hour, which is in agreement with the general thermal history of the ureilite parent body with the quenching episode due to the impact break-up of the parent body while it was still hot. The asteroid 2008TC3 implies an origin from the loosely-packed brecciated surface of the re-accreted body composed of fragments with different degrees of quenched thermal history that were produced by the impact break-up of the original ureilite parent body.