Morphological and compositional investigation of Krieger crater (Moon)

Krieger crater is an impact lunar crater located in the Oceanus Procellarum, on the western near-side of the Moon. It is partly overlaid by Van Biesbroeck impact crater on the southern rim; a sinuous rille, Rima Krieger, originates from the western rim. Krieger is surrounded by wrinkle ridges, linear structural features, and different mare materials. In order to investigate the geomorphological setting, we used remote sensing datasets from Lunar Reconnaissance Orbiter and Kaguya for photogeological and topographic analysis through high-resolution imagery and DEM, and Moon Mineralogy Mapper hyperspectral data for surface compositional investigation. Krieger is characterized by a polygonal-shaped rim, an asymmetrical ejecta blanket, oriented north-south (indicating a potential oblique impact) and a complex floor configuration, with morphologic features, like hummocks, large mounds, a possible central peak, and unclear concentric fractures. Both Krieger and Van Biesbroeck walls exhibit melt coating features, fresh exposed materials, melt veneers, and mass wasting morphologies. Hyperspectral analysis determined several surface mineral compositions, differing especially in olivine and glass content. Important compositional differences were observed in the Krieger floor, where mare-like basalts have been detected, suggesting an internal post-impact volcanism which resulted in the breaching of the western rim and subsequent lava flow outside the crater, originating Rima Krieger. We found also the contamination of highland material in the southern ejecta, potentially derived from the Aristarchus crater impact. Thus, this complex geological setting suggests that post-impact modification processes, including volcanism, tectonic movements and later impacts, played a key role in shaping up the present Krieger crater.