The brittle boulders of dwarf planet Ceres

TL;DR

This study maps and analyzes the properties of boulders on Ceres, revealing their distribution, mechanical weakness, potential ice content, and unique size distribution, which differ from those on Vesta and suggest specific geological processes.

Contribution

It provides the first comprehensive mapping and characterization of Ceres' boulders, highlighting their distribution, age, mechanical properties, and size distribution, with implications for their composition and formation.

Findings

Boulders are more numerous at high latitudes.

Maximum boulder lifetime is approximately 150 million years.

Boulder size distribution follows a Weibull distribution, not a power law.

Abstract

We mapped all boulders larger than 105 m on the surface of dwarf planet Ceres using images of the Dawn framing camera acquired in the Low Altitude Mapping Orbit (LAMO). We find that boulders on Ceres are more numerous towards high latitudes and have a maximum lifetime of $150 \pm 50$ Ma, based on crater counts. These characteristics are distinctly different from those of boulders on asteroid (4) Vesta, an earlier target of Dawn, which implies that Ceres boulders are mechanically weaker. Clues to their properties can be found in the composition of Ceres' complex crust, which is rich in phyllosilicates and salts. As water ice is though to be present only meters below the surface, we suggest that boulders also harbor ice. Furthermore, the boulder size-frequency distribution is best fit by a Weibull distribution rather than the customary power law, just like for Vesta boulders. This finding is robust in light of possible types of size measurement error.