Deriving Morphometric Parameters and the Simple-to-Complex Transition Diameter From a High-Resolution, Global Database of Fresh Lunar Impact Craters (D ≥ ~ 3 km)

摘要

We compiled a high-resolution, global lunar impact crater database composed of 5,505 pristine craters ≥ ~3 km. This database contains detailed morphometric data, and their trends are examined with best-fit power-laws. We compared several different functions for simple, transitional, and complex craters to report one best-fit representation. We integrated transitional craters into these fits as an independent crater class. Transitional craters are in a transitional state, between simple and complex craters. They are devoid of a central uplift and terraces but show wall slumping and a flat floor. In regard to depth-diameter relationships, simple craters exhibit similar scaling all over the Moon, whereas larger craters are different in highland and mare regions. In the present work, we sought the best representation of the simple-to-complex transition diameter. The intersection of simple power-law fits for simple and complex crater populations is shown to be a poor representation of the transition diameter. We used a misclassification method for finding transition diameters. This process reveals a transition fromsimple to transitional craters at diameters of ~17 km (highland) and ~14 km (mare). Transitional morphology is replaced by complex morphology at diameters of ~ 28 km (highland) and ~ 24 km (mare). The lower transition diameters of mare craters are attributed primarily to the layered mare basalts, which enables an earlier onset of crater modification. We also analyzed the relationship between aspect ratio and depth-diameter ratio of simple craters: Simple craters with ε ≥ 1.1 are significantly shallower in depth/diameter plots than craters with ε < 1.1.