Characterization of the MASCOT landing area by Hayabusa2

TL;DR

This study compares the MASCOT landing site on asteroid Ryugu with the average surface to determine if it is representative, using multi-instrument observations, and finds the site and rock are generally typical of Ryugu.

Contribution

It provides a detailed analysis of the MASCOT landing area, demonstrating its spectral and thermophysical similarity to the average Ryugu surface, clarifying the discrepancy with returned samples.

Findings

MASCOT landing site is spectrally and thermally similar to Ryugu's average surface.

The MASCOT rock's spectral properties are likely average, but its thermal inertia may be higher.

Atypical particles in samples may be inclusions in the MASCOT rock.

Abstract

Context. After landing on C-type asteroid Ryugu, MASCOT imaged brightly colored, submillimeter-sized inclusions in a small rock. Hayabusa2 successfully returned a sample of small particles from the surface of Ryugu, but none of these appear to harbor such inclusions. The samples are considered representative of Ryugu. Aims. To understand the apparent discrepancy between MASCOT observations and Ryugu samples, we assess whether the MASCOT landing site, and the rock by implication, is perhaps atypical for Ryugu. Methods. We analyzed observations of the MASCOT landing area acquired by three instruments on board Hayabusa2: a camera (ONC), a near-infrared spectrometer (NIRS3), and a thermal infrared imager (TIR). We compared the landing area properties thus retrieved with those of the average Ryugu surface. Results. We selected several areas and landforms in the landing area for analysis: a small crater, a collection of smooth rocks, and the landing site itself. The crater is relatively blue and the rocks are relatively red. The spectral and thermophysical properties of the landing site are very close to those of the average Ryugu surface. The spectral properties of the MASCOT rock are probably close to average, but its thermal inertia may be somewhat higher. Conclusions. The MASCOT rock can also be considered representative of Ryugu. Some of the submillimeter-sized particles in the returned samples stand out because of their atypical spectral properties. Such particles may be present as inclusions in the MASCOT rock.