Measurement and Analysis of Lunar Basin Depths from Clementine Altimetry

Abstract

Altimetric profiles from the Clementine LIDAR are used to calculate the depths of 29 large craters and basins on the Moon. Plotting the depths of the best preserved structures together with values for simple and complex craters measured in pre-Clementine studies reveals an inflection in the depth/diameter (d/D) curve in addition to the one revealed by pre-Clementine data. This inflection occurs in the diameter range that corresponds to the morphologic transition from complex crater to basin. The best empirical power law fit for basin depths is log10(d) = 0.41 × [log10(D)]0.57. This relationship is characterized by a lower slope than that for complex craters, demonstrating that this morphologic transition corresponds to a further decrease in the depth of an impact structure relative to its diameter with increasing size. Qualitative consideration of possible causes for the second inflection leads to the conclusion that it is most likely a consequence of a short-term modification mechanism that influences fundamental crater morphology, such as the increasing influence of gravity with diameter. Thicknesses of maria in the major basins are calculated by assuming that their unfilled depths would follow thed/Drelation. Results are compared with previous estimates and yield thicknesses that are generally greater than those determined by studies of flooded craters and less than those obtained from analysis of gravity. © 1998 Academic Press.