Depth-to-diameter Ratios of Fresh Craters on the Moon and Implications for Surface Age Estimates

Abstract

The depth-to-diameter (d/D) ratios of small lunar craters (D < 400 m) can be used to determine important properties of the upper regolith, specifically material strength or thickness. The d/D is also an important component of topographic diffusion models that describe how different erosive processes influence and change the topography of a surface over time, and these models have been applied to estimate surface ages. These models must make assumptions regarding rates of erosion and the initial d/D of a crater. Previous works investigating d/D of small craters, which use various methodologies to calculate depth, typically assume that a fresh appearing crater is a young crater. Work presented here provides d/D measurements of known—rather than assumed—young, meter-scale craters to provide better constraints on small crater depths and to help further our understanding of lunar surface ages and upper regolith properties. Given the interest in impact crater modification at small, human scales on the Moon and the wide range of assumptions built into topographic diffusion models and their predictions, understanding whether the results for initial d/D from past work hold up under different analyses is critical. We observed no distinct trends in d/D for small, young craters and report a wide range of d/D from 0.08 to 0.215, in contrast with past work that derived different averages based on crater size. The variation in d/D may correspond to heterogeneous regolith properties or be a result of a data source artifact.