The evolution of lunar rock size-frequency distributions: An updated model

The model for the catastrophic rupture of rocks on the lunar surface [1] is revisited by considering new functions describing rock shattering by impacts and size-frequency distributions of meteoroids. The input functions are calibrated by comparing the model block size–frequency
distributions with the measured size–frequency distribution of ejecta blocks around Tycho crater, which formation age is known. We find that the evolution of lunar block size–frequency distribution in the range 1–50 m is as follow: For young (≤ 50
Myr) population, the size–frequency distribution is best approximated by a power law, whereas for older populations, the extrapolation at small diameters is best performed by an exponential
distribution. New destruction rates are in better agreement with recent measurements [2,3] compared to the original model. For rocks above ~5 cm the survival time increases with increasing size, whereas for rocks below ~5 cm the survival time slightly increases with decreasing size. The updated model allows the estimation of both the exposure age and the initial abundance of a block field using the measurement of a block size–frequency distribution from LROC/NAC images.

References: [1] Hoerz et al., 1975, The Moon 13, 235–258. [2] Basilevsky et al., 2013, PSS, 89 (118–12). [3] Ghent et al., 2014, doi:10.1130/G35926.1.