Mapping lunar mare basalt units in mare Imbrium as observed with the Moon Mineralogy Mapper (M³)

We examine compositional variations of volcanic units in the Imbrium basin using spectral observations from the Moon Mineralogy Mapper (M³) instrument on board the Chandrayaan-1 spacecraft. The spectral range of M³ reflectance measurements from 400 to 3000 nm is well-suited to study distinctive absorption bands near 1000 and 2000 nm resulting from mafic minerals in lunar basaltic flows. Eighty-three units with various mineralogical compositions were identified, and spectroscopic analyses were used to map variations in olivine and pyroxene content within basalts emplaced in the Imbrium basin. The results exhibit a more precise mapping of basaltic flow units with M³ data based on their better spatial and spectral range in comparison to previous available datasets. Nevertheless, there is a general correlation between units mapped in this work and previous studies. Moreover, the results tend to indicate an increase in olivine abundances in the stratigraphically younger high-Ti basalts compared to the older low-Ti basalts. Therefore, on the basis of M³ data, we refine previous spectral maps that have been used, for example, to determine first order homogenous units for crater size-frequency distribution measurements.