Degradation Rate and Lifetime of Small Impact Craters on the Moon

Abstract

Knowledge of crater degradation rates on the Moon is fundamental for dating individual craters, understanding material transport, and investigating crater equilibrium, with broader implications for water ice exploration, regolith evolution, and impact flux reconstruction. However, direct observational constraints on the degradation rates of hundred‐meter‐scale lunar craters remain scarce, and regional variations between mare and highland terrains are poorly quantified. Here, we measure the diameters and depths of 56,229 small impact craters across the Apollo, Luna, and Chang’E landing regions using high‐resolution optical and topographic data. We then systematically simulate the production and evolution of crater populations from geological unit emplacement to the present, accounting for both diffusive degradation and catastrophic obliteration. By comparing observations with forward simulations, we provide the most extensive observational constraints to date on the degradation rates and lifetimes of small craters with diameters of 50–500 m. At these scales, the estimated topographic diffusivities increase from 0.62 to 2.33 /Myr in the maria and from 2.27 to 4.54 /Myr in the highlands. Regional variations in degradation rates are most strongly associated with meter‐scale slope rather than adopted proxies for target properties. The inferred lifetimes imply that subhectometer micro cold traps are short‐lived (<100 Myr) and thus host only recently delivered water ice, whereas larger cold traps of several hundred meters can persist over geological timescales and are favorable for water ice accumulation. Our results further indicate that crater equilibrium at small diameters is achieved mainly through diffusive degradation rather than superposition, and that equilibrium crater abundance is expected to vary across the Moon.