A mid-infrared study of synthetic glass and crystal mixtures analog to the geochemical terranes on mercury

The MERTIS (MErcury Radiometer and Thermal Infrared Spectrometer) onboard of the BepiColombo ESA/JAXA mission to Mercury will map the surface of Mercury in the wavelength range of 7–14 μm and for the interpretation of these spectra a database of analog materials is needed. We analyzed bulk grain size fractions of a series of analog materials relevant to the distinct terranes of Mercury in diffuse reflectance in the mid-infrared (2.5 μm to 18 μm). Mineral mixtures cover a wide range of modal amounts of forsterite, enstatite, diopside and plagioclase, the resulting spectra can be divided into three distinct groups: (1) is dominated by a single glass feature, (2) by forsterite bands, and (3) by pyroxene bands. Despite often high contents, plagioclase features, are usually ‘overprinted’ by forsterite and pyroxene bands.