The Crust of the Moon as Seen by GRAIL

Abstract

High resolution gravity data obtained from the dual GRAIL spacecraft are providing an unprecedented view of the Moon’s crust. The bulk density of the highlands crust is found to be 2550 kg m ⁻³, significantly lower than generally assumed, and when combined with remote sensing and sample data, an average crustal porosity of 12% to depths of at least a few km is required. Lateral variations in crustal porosity correlate with the largest impact basins, whereas lateral variations in crustal density correlate with crustal composition. The low bulk crustal density allows construction of a global crustal thickness model that satisfies the Apollo seismic constraints, and with an average crustal thickness between 34 and 43 km, the bulk refractory element composition of the Moon is not required to be enriched with respect to Earth.