Variations in Lunar Crater Populations Due to Target Properties

Crater chronology models rely on correlating observed crater size-frequency distributions (CSFDs) on the ejecta blankets of Copernican-age craters with cosmic-ray exposure ages of samples acquired by Apollo missions. However, these crater populations are known to vary on the ejecta of these craters. One explanation is that impact melts, boulders, and other variations in material properties can influence the scaling of impact craters. We conduct crater counts on the ejecta of several Copernican-age craters and find that crater densities vary with the thermophysical properties of the ejecta as observed by the Lunar Reconnaissance Orbiter Diviner instrument, providing evidence that the strength of ejecta materials can have a significant influence on CSFDs. Specifically, we find that as Diviner-derived rock abundance increases, the spatial density of craters decrease. Absolute model ages are affected as areas of higher rock abundance yield younger ages. This suggests terrain properties should be taken into consideration when deriving absolute model ages.