Depths of Copernican Craters on Lunar Maria and Highlands

Abstract

We present a study on the relationship between the ratio of the depth of a crater to its diameter and the diameter for lunar craters both on the maria and on the highlands. We consider craters younger than 1.1\xa0billion years in age, i.e. of Copernican period. The aim of this work is to improve our understanding of such relationships based on our new estimates of the craters’s depth and diameter. Previous studies considered similar relationships for much older craters (up to 3.2\xa0billion years). We calculated the depths of craters with diameters from 10 to 100\xa0km based on the altitude profiles derived from data obtained by the Lunar Orbiter Laser Altimeter (LOLA) onboard the Lunar Reconnaissance Orbiter (LRO). The obtained ratios h / D of the depths h of the craters to their diameters D can differ by up to a factor of two for craters with almost the same values of diameters. The linear and power approximations (regressions) of the dependence of h/D on D were made for simple and complex Copernican craters selected from the data from Mazrouei et al. (Science 363:253–255, 2019) and Losiak et al. (Lunar Impact Crater Database, 2015). For the separation of highland craters into two groups based only on their dependences of h/D on D , at D \u2009<\u200918\xa0km these are mostly simple craters, although some complex craters can have diameters D \u2009≥\u200916\xa0km. Depths of mare craters with D \u2009≤\u200914\xa0km are greater than 0.15 D . Following Pike’s (Lunar Planet Sci XII:845–847, 1981) classification, we group mare craters of D \u2009<\u200915\xa0km as simple craters. Mare craters with 15\u2009<\u2009 D \u2009<\u200918\xa0km fit both approximation curves for simple and complex craters. Depths of mare craters with D \u2009>\u200918\xa0km are in a better agreement with the approximation curve of h/D versus D for complex craters than for simple craters. At the same diameter, mare craters are deeper than highland craters at a diameter smaller than 30–40\xa0km. For greater diameters, highland craters are deeper. The values of h/D for our approximation curves are mainly smaller than the values of the curve by Pike (in: Roddy, Pepin, Merrill (eds) Impact and explosion cratering: planetary and terrestrial implications, University of Arizona Press, Tucson, 1977) at D \u2009<\u200915\xa0km. Only for mare craters at D \u2009<\u200911\xa0km, our approximation curve is a little higher than the curve by Pike (1977). For our power approximations, the values of h/D obtained for complex craters are greater than those obtained by Pike (1981) at D \u2009>\u200953\xa0km for highland craters, and at D \u2009<\u200980\xa0km for mare craters.