The Evolution of Rock Size-Frequency Distribution on the Moon: Effects of Rock Strength and Fragmentation Products on Centimeter-Scale Abundances

Abstract

Rock abundances on the Moon represent both an opportunity to understand the history of the surface and of the regolith and a hazard to lander missions. While rock erasure by meteoroid bombardment is known to modify rock size˗frequency distributions, the interplay between rock erasure and rock exposure by impact cratering, and the resulting net rock abundance, is not known. Leveraging a coupling between modeling and optical imagery from the lunar orbit, we calculate new rock lifetimes that consider the specific shattering energy and the fragments produced by boulder shattering. We find differences between the estimated and expected specific shattering energy (Q_s*), likely suggesting incomplete understanding of the scaling of the shattering energy with velocity and size. We find that the decrease in rock abundances with time on crater ejecta occurs faster than previous estimates based on thermal infrared data.