Temporal Evolution of Crater Populations Formed on Different Facies of Lunar Complex Craters

The formation of a large complex crater is accompanied by the simultaneous formation of coeval sub-geological units that have diverged physical properties, such as a central melt pool and an ejecta blanket. Crater populations formed on different geological units of a given young complex craters usually exhibit different size–frequency distributions (SFDs), but the difference disappears for relatively old craters, e.g., the Copernicus crater with an age of about 800 million years ago (Ma). However, there is a lack of temporal and theoretical constraints on the evolutionary pathway connecting these two SFD end-member states. Here, by observing crater SFDs of complex craters with ages between about 75 Ma and 871 Ma, we find a decrease in the crater SFD difference between coeval geological units with increasing age. The time-dependent crater SFD difference is consistent with modeled production functions with consideration of time-dependent target physical properties. The time dependence of target properties potentially arises from impact-induced damage, which efficiently converts coherent melt into ejecta-like fragments. Our results also imply that the proportion of self-secondary craters to the diameter ≥120 m crater population superposing on the facies of lunar complex craters with age older than crater Tycho is possibly less than 50% and decreases with time.