Impact-Caused Regolith Reworking within the Polar Regions of the Moon

The paper estimates the minimum, mean and maximum thickness of regolith and degree of its impact-caused reworking as a function of depth based on spatial density of small impact craters for the floors of polar craters Shoemaker, Sverdrup and Shackleton and for the landing sites of Luna-16 , - 17 , and - 24 . Key parameter for these calculations is D cr , the boundary diameter between the equilibrium and non-equilibrium parts of crater population. It was found to be 80 m for the Luna-24 site and crater Shackleton, 100 m for the Luna-16 and - 17 sites, 350 m for crater Sverdrup and 1000 m for crater Shoemaker. The median thicknesses of regolith for these areas were found to be 3,2, 4, 14, and 40 m, respectively. For these areas, the number of the reworking events was found to be 1, 6, 2, 7, and 20 for the 2 m depth, 3, 4, 14 and 40 times for the 1 m depth, 6, 8, 28 and 80 times for the 0,5 m depth, 16, 20, 70, and 200 times for the 0.2 m depth, and 64, 80, 280, and 800 times for the 0.05 m depth. These reworking impacts should mechanically mix the polar regolith and cause multiple local vaporization / condensation of the frozen volatiles leading to their physico-chemical differentiation.