Using the modified Gaussian model to extract quantitative data from lunar soils

Abstract

The Lunar Soil Characterization Consortium (LSCC) has examined and characterized a suite of lunar soils with a wide range of compositions and maturities. The purpose of this study is to compare the Vis/NIR spectral properties of these lunar soils with their petrologic and chemical compositions using the modified Gaussian model (MGM) to obtain quantitative data about the character of relatively weak near‐infrared absorption bands. Useful compositional information can be extracted from high‐quality soil spectra using the MGM. The model had some difficulty fitting absorption bands in the 2 μm region of the lunar spectrum, but bands in the 1 and 1.2 μm regions provided physically realistic results. The model was able to distinguish high‐Ca and low‐Ca pyroxenes in the LSCC suite of lunar soils in the appropriate relative abundance. In addition, unexpected insights into the nature and causes of absorption bands in lunar soils were identified. For example, at least two distinct absorption bands are required in the 1.2 μm region of the spectrum, and neither of these bands can be attributed to plagioclase or agglutinates, but are found instead to be largely due to pyroxene.