Constraints on olivine-rich rock types on the Moon as observed by Diviner and M³: Implications for the formation of the lunar crust

We place upper limits on lunar olivine abundance using midinfrared (5–25 µm) data from the Lunar Reconnaissance Orbiter Diviner Lunar Radiometer Experiment (Diviner) along with effective emissivity spectra of mineral mixtures in a simulated lunar environment. Olivine-bearing, pyroxene-poor lithologies have been identified on the lunar surface with visible-near-infrared (VNIR) observations. Since the Kaguya Spectral Profiler (SP) VNIR survey of olivine-rich regions is the most complete to date, we focus this work on exposures identified by that study. We first confirmed the locations with VNIR data from the Moon Mineralogy Mapper (M³) instrument. We then developed a Diviner olivine index from our laboratory data which, along with M³and Lunar Reconnaissance Orbiter Camera wide-angle camera data, was used to select the geographic area over which Diviner emissivity data were extracted. We calculate upper limits on olivine abundance for these areas using laboratory emissivity spectra of anorthite-forsterite mixtures acquired under lunar-like conditions. We find that these exposures have widely varying olivine content. In addition, after applying an albedo-based space weathering correction to the Diviner data, we find that none of the areas are unambiguously consistent with concentrations of forsterite exceeding 90 wt %, in contrast to the higher abundance estimates derived from VNIR data.