Double Shadows at the Lunar Poles

Abstract

Topographic depressions within permanently shadowed regions (PSRs) on low-obliquity planetary bodies can be shielded not only from direct illumination, but also from scattered sunlight and thermal emission from nearby sunlit surfaces. We apply an illumination model to high-resolution topography data to produce the first map of double shadows at the lunar poles. The total doubly shadowed area resolved at the 30 m scale is 1.47 km2 in the northern hemisphere and 5.37 km2 in the southern hemisphere, predominantly contained within small craters on the floors of large permanently shadowed craters. In total, ∼0.04% of PSR area is permanently double shadowed, but the largest double shadows are nearly 600 m across, potentially large enough to be resolved in remote sensing temperature measurements. In the absence of secondary heating sources, double shadows are predicted to be significantly colder than singly shadowed areas and could sequester highly volatile compounds like carbon dioxide. Future in situ investigation of the regions identified in this work can elucidate the origin and distribution of the Moon’s most volatile deposits.