Variation of the lunar highland surface roughness at baseline 0.15 - 100 km and the relationship to relative age

Abstract

We report the surface roughness analysis of the lunar highlands for the baseline range 0.15-100km. We use the Median Differential Slope (m) to investigate the scale dependency of the roughness and derive the global (m) distribution from SELENE Laser Altimeter and Terrain Camera data. While (m)(l) versus baseline l (km) plots vary among different highland types, all highlands commonly show a peak at 3-30km. The Pre-Nectarian surface shows a relatively large (m)(20-30km). Our analysis is supported by the simulation of synthetic surface cratering models and crater statistics. In our simulation, a peak of (m)(30km) is successfully reproduced. The actual crater density shows good correlation with an empirical roughness indicator. However, a large part of the Nectarian surface shows a peak at 6-9km baseline. This peak may be caused by secondary craters and ejecta deposit textures from the Nectarian system basins.