Traces of water in lunar meteorite and the water rich lunar mantle

Abstract

Water content of the Moon was thought to be less than 1 ppb, but water-rich apatite and melt inclusion were recently discovered in the lunar samples, speculating water content of 1-100 ppm order in the mantle. Here, we measured infrared spectra of clinopyroxene and olivine in lunar mantle-derived gabbroic/basaltic breccia of NWA 2727 meteorite, with KREEP component and 2.9 Ga crystallization age, to estimate water content in the mantle, directly. Only clinopyroxene and olivine in the gabbroic clasts contain 518 ppm and 484 ppm water, respectively, implying a wet lunar mantle with 494 ppm water, comparable to terrestrial mantle.