Slopes of Lunar Crater Size-Frequency Distributions on Exterior Impact Melt Deposits of Young Craters

Abstract

Lunar impact craters can be used as a tool to derive information about the timing and sequence of the emplacement of geologic units and surface processes on the Moon. The production function (PF) derived from crater size-frequency distribution (CSFD) measurements is an essential component in determining the model age of a geologic surface. The PFs of Neukum (1983) and Neukum et al. (2001), https://doi.org/10.1007/978-94-017-1035-0_3 are defined only over a crater diameter range between 10 m and 300 km and are among the most frequently used PFs. However, a potential extension of the valid crater diameter range to smaller craters may be possible due to the availability of high-resolution image data, and a larger number of small craters could reduce the statistical errors in age determinations. To evaluate whether CSFD measurements with craters ≤10 m are suitable for inclusion in a PF, we complement the investigation of ejecta blankets (Oetting et al., 2023, https://doi.org/10.1029/2023je007816) by analyzing the CSFD slopes of small craters formed on impact melt deposits of young Copernican-aged craters Tharp, Korolev Z, Thales, and Glushko. The resulting CSFD slopes are slightly steeper for craters between 10 and 20 m than the proposed cumulative −3 slopes by Neukum (1983) and Neukum et al. (2001), https://doi.org/10.1007/978-94-017-1035-0_3. The CSFD slope for craters ≤10 m is shallower than −3. In this study, the CSFD slopes are derived from unbinned data, but we present our CSFD measurements in both unbinned and binned form. Our results indicate that small crater diameters (≤10 m) can be included for extending a PF.