The structural and spectroscopic effects of space weathering of C-type asteroid regolith documented by Ryugu sample A0112.

Abstract

Fragments of the near-Earth C-type asteroid 162173 Ryugu were brought back to Earth as part of JAXA’s Hayabusa2 sample return mission (e.g., [1,2]). Our consortium received Chamber A sample A0112, collected from Ryugu’s immediate surface, for non-destructive spectral and microchemical analysis. Our aim is to assess the effects of space weathering, the gradual alteration of airless planetary surfaces by micrometeoroid bombardment and influx of solar wind ions and cosmic rays [3], on carbonaceous asteroid surfaces. Because space weathering alters the optical properties of space-exposed regolith, understanding space weathering is critical for interpretation of remote-sensing data obtained from planetary surfaces and for matching various meteorite types to potential parent bodies. While the effects of space weathering on anhydrous regoliths are well understood (e.g., [4–6]), space weathering of hydrous, carbonaceous-chondrite-like (C-type) asteroidal surfaces is poorly understood so far [7,8].