Elemental abundance variations at small-scale in Ryugu grains

Abstract

Since small bodies like asteroids preserved important clues to elucidate the planetary processes within the protoplanetary disk, sample return missions represent a valuable opportunity to study pristine materials. Samples returned from asteroid Ryugu have been reported to exhibit small-scale chemical heterogeneity which likely stems from secondary processes in the parent body, such as aqueous alteration. Therefore, this study aims to investigate the small-scale variation in the elemental abundance of Ryugu to gain better insights into the history of its parent body. For this purpose, the abundance of 54 elements were measured in eight Ryugu grains from the first touchdown. The bulk chemical compositions of the eight grains show a wide variation for most elements. In particular, P, Ca, Mn, Sr, Y, and rare earth elements exhibit broader ranges compared to the average CI composition. The enrichment or depletion in these elements can be attributed to the presence of secondary minerals, such as carbonates and phosphates, formed during aqueous alteration in the parent body.