Remote sensing studies of the Orientale Region of the Moon: A pre‐Galileo view

Abstract

We have acquired both an extensive data base of visible and near‐infrared spectra and multispectral images (ultraviolet and visible) of the Orientale region of the Moon. Our results show that the eastern Inner Rook Mountains are composed of anorthosite. Portions of the main ring of the Humorum basin and the inner ring of Grimaldi are also composed of anorthosite. Other deposits within the Orientale basin and the major ejecta unit outside the basin are dominated by noritic anorthosites; mature surfaces have spectra nearly identical to those taken of areas in the vicinity of the Apollo 16 site. Thus, it appears that Orientale ejecta are more mafic than materials that are thought to have originated at depth (i.e., the anorthosites in the Inner Rook Mountains). There are large areas that have mare basalt signatures mixed with highland rock types, indicating the existence of ancient, pre‐Orientale mare volcanism. Present mare surfaces in the Orientale region contain basalts of intermediate to very low TiO 2 content.