A new compositional, mineralogical and chronological study of the Leibnitz crater within the SPA basin

Abstract

Leibnitz is an impact crater 237 ​km in diameter located on the lunar farside within the South Pole–Aitken (SPA) basin. It shares much of its southern rim with the Von Kármán crater (186 ​km in diameter), which is currently the focus of in situ exploration by the Yutu-2 rover, part of the Chang'e−4 mission. This complementary study analyzes Leibnitz's surface materials mineralogy and age using remote sensing data. We focused on the spectral information from 95 fresh craters within Leibnitz to minimize the effects of weathering on the exposed materials. Subsequently, we employed the Modified Gaussian Model to derive a distribution map for the high to low Ca pyroxene ratio values. Finally, we derived absolute model age estimations of the mare basalts using the lunar crater chronology method. A new geologic map of the Leibnitz crater summarizes the results of this study. The results show that the interiors of Von Kármán and Leibnitz share a degree of similarity in mineral composition, with strong absorption features around the 1 ​μm and 2 ​μm bandcenters, due to the spectral dominance of mafic minerals. The ejecta from the adjacent Finsen crater have higher Ca/Fe and HCP/LCP ratios than the exposed materials of the Leibnitz crater. This study also finds evidence to support an older age of formation of the crater than age estimates to date from previous studies of the Leibnitz crater.