Small lunar crater degradation and crater’s SFD and lifetime

Small lunar craters are not killed by newer craters of a similar size (as it was assumed initially), but are slowly degrading from the initial large to a small depth/diameter (d/D) ratio. In the current project we make the comparative analysis of available data on the areal cratering density for selected regions, including craters, dated with returned Apollo samples. In the first approximation we confirm Neukum’s chronological model. At the same time, we find new possible uncertainties in estimates of the crater retention age (due to crater degradational widening is estimated). The problem not resolved properly to date is the difference in visible degradation rate in different Apollo landing sites. We review briefly mechanical models of the lunar crater degradation. The main volume of data used in the presentation is compiled in a recently published paper [Ivanov, B.A. Size-frequency distribution of small lunar craters: widening with degradation and crater lifetime. Solar System Research, 2018, vol. 52, no.¨1, pp. 1-25].