Pure lunar anorthosite

Based on analyses of lunar samples of anorthosite, the igneous rock made up mainly of plagioclase feldspar that predominates there, the light-coloured crust of the lunar highlands is thought to have been formed by the crystallization and flotation of plagioclase from a global magma ocean. The exact mechanism by which such a crust formed remains a matter for debate. Spectroscopic data from SELENE, the main orbiter component of the Japanese KAGUYA lunar mission, have now been used to produce a clear and high spatial resolution view of the composition of the lunar crust. The data, from 69 different locations, reveal the widespread existence of virtually pure — 100% plagioclase — anorthosite. This contrasts to previous estimates of 82 to 92 vol% plagioclase, providing a valuable constraint on models of lunar magma ocean evolution.