Spectrophotometric analysis of the Ryugu rock seen by MASCOT: Searching for a carbonaceous chondrite analog

TL;DR

This study uses spectrophotometric analysis of a Ryugu rock to identify potential carbonaceous chondrite analogs, revealing its typical reflectance, inclusion characteristics, and possible links to specific meteorite groups.

Contribution

It provides the first detailed spectrophotometric analysis of a Ryugu rock, identifying its reflectance, inclusion properties, and potential meteorite analogs, advancing understanding of asteroid composition.

Findings

Rock's reflectance matches Ryugu's average

Inclusions are brighter and vary in spectral slope

Possible link to CR2 and CV3 meteorites

Abstract

We analyze images of a rock on Ryugu acquired in situ by MASCam, camera of the MASCOT lander, with the aim of identifying possible carbonaceous chondrite (CC) analogs. The rock's reflectance ($r_{\rm F} = 0.034 \pm 0.003$ at phase angle $4.5^\circ \pm 0.1^\circ$) is consistent with Ryugu's average reflectance, suggesting that the rock is typical for this asteroid. A spectrophotometric analysis of the rock's inclusions provides clues to CC group membership. Inclusions are generally brighter than the matrix. The dominant variation in their color is a change of the visible spectral slope, with many inclusions being either red or blue. Spectral variation in the red channel hints at the presence of the 0.7~$\mu$m absorption band linked to hydrated phyllosilicates. The inclusions are unusually large for a CC; we find that their size distribution may best match that of the Renazzo (CR2) and Leoville (CV3) meteorites. The Ryugu rock does not easily fit into any of the CC groups, consistent with the idea that typical Ryugu-type meteorites are too fragile to survive atmospheric entry.