Spectral reflectance studies of the Grimaldi Region of the Moon

Abstract

Near‐infrared reflectance spectra were used to investigate the composition and origin of the various geologic units in the Grimaldi region as well as the stratigraphy of the Grimaldi pre‐impact target site. The results of our spectral analysis indicate that the portions of the Hevelius Formation that occur in the Grimaldi region are composed of noritic anorthosite and anorthositic norite. Gabbroic material was excavated from beneath Orientale‐related units by small impact craters in three areas in the Grimaldi region. The primary ejecta deposits of the Grimaldi basin as well as the pre‐Orientale floor unit are dominated by noritic anorthosite and anorthositic norite. The peak ring of Grimaldi is composed, at least in part, of pure anorthosite. The anorthosites on the inner ring and elsewhere within Grimaldi were derived from a layer of pure anorthosite that exists at depth beneath a more pyroxene‐rich unit.