Statistical estimates of rock-free lunar regolith thickness from Diviner

The thickness of the lunar regolith has been previously estimated using seismic, radar, and crater morphology data to be on the order of tens of meters. In this study, we use rock abundance measurements from the Diviner radiometer aboard the Lunar Reconnaissance Orbiter (LRO) to provide new estimates of rock-free regolith thickness in recently-formed impact craters. Diviner cold spots have been shown to last no longer than a few 100 kyr, and thereby point to fresh craters on the moon. Trends in Diviner data also show that deeper cold spot craters have rockier ejecta. We employ statistical analyses to show that cold spot craters in the lunar mare have rockier ejecta at smaller excavation depths when compared to those in the highlands. We estimate that the average rock-free regolith is 12.6 m thick in the mare and 18.5 m thick in the highlands, which is consistent with previous estimates. We expect these values will be highly variable due to differences in regolith development and overturn across the moon.