Using boulder tracks as a tool to understand the bearing capacity of permanently shadowed regions of the moon

Abstract

The polar regions of the Moon contain areas that never experience sunlight, known as permanently shadowed regions (PSRs). These regions are thought to contain uneven distributions of water ice deposits. To access PSRs and their possible water deposits, we must first understand the strength of the soil at these locations to safely traverse them. Thirteen boulder tracks were identified on the edge of, or within, PSRs in the lunar south polar region using images taken by the Lunar Reconnaissance Orbiter. These images were processed to enable the measurement of boulders and their associated tracks. The tracks identified within PSRs have similar appearances to those identified outside PSRs in other regions on the Moon. The strength of soil within PSRs was estimated from the measurements taken and was shown to be at least as strong as highland and mare regions of the Moon at relatively shallow depths, although the studied PSRs show no evidence for the presence of water ice. Analysis shows that PSRs of the type measured here should be able to bear rovers at depths of at least ~30 cm. In situ measurements are required to confirm and better understand the mechanical behavior of PSR regolith at shallow depths.