Modeling the Evolution of Lunar Regolith: 1. Formation Mechanism Through Individual Simple Impact Craters

The production, distribution, and evolution of lunar regolith are critical in deciphering the lunar bombardment history and comprehending the transport of materials across the lunar surface, which are still not well understood. In this study, we conducted a comprehensive investigation of factors influencing the production and distribution of lunar regolith by individual simple craters. Combining our results for the impact‐generated regolith volume with a lunar production function, we developed an analytical model to describe the regolith growth process. We found that the strength of bedrock significantly affects the crater size and hence the volume of regolith produced especially for subdecameter impactors. The regolith volume produced by an individual impact crater is quantitatively characterized as a function of crater diameter and preimpact regolith thickness. This regolith production is primarily determined by how much bedrock is shattered, followed by the impact‐induced volume change of target material and lastly by the regolith volume created by secondary cratering processes. When a single crater forms, preimpact regolith thickness greatly affects the regolith distribution pattern; a larger fraction of the regolith will be distributed outside the crater rim for a deeper preimpact regolith layer. Our regolith evolution model can serve as a good first‐order estimation of the regolith growth process that provides better constraints on the regolith buffering trend than previous studies. This model also suggests that, when ignoring the contribution from large, distant impacts, the regolith growth process is dominated by impact craters at scales from a meter to a few hectometers. Plain Language Summary Lunar regolith refers to the fine‐grained surficial layer of fragmental debris on the Moon that is primarily formed by continuous impact events. Knowledge of regolith production, distribution and evolution is important for revealing the impact history of the Moon and the mixing and transport processes of materials on the lunar surface. In this study, we investigated how individual impact craters produce and distribute regolith and developed an analytical regolith evolution model to describe the process of regolith growth. We found that the strength of bedrock greatly affects the regolith production especially for subhectometer craters. The regolith volume is mainly determined by how much bedrock is shattered by impact cratering, but it also depends upon the