Thermal infrared spectroscopy to investigate the composition of mercury – The MERTIS instrument on BepiColombo

Abstract Telescopic measurements have shown that the surface composition of Mercury can be derived only indirectly from VIS-NIR-spectra: the spectral slopes and the absence of any feature in the range from 0.5 to 1 μm indicate feldspar as main component. [Hapke, B., Danielson, G.E., Jr., Klaasen, K., Wilson, L. Photometric observations of Mercury from Mariner 10. J. Geophys. Res. 80, 2431–2443, 1975; Hapke, B. Interpretations of optical observations of Mercury and the moon. Physics of the Earth and Planetary Interiors, vol. 15, no. 2–3, pp. 264–274, 1977.] suggested based on the analysis of albedo and color relationships on Mariner 10 images that very low contents of FeO (at about 3–6 wt%) and TiO 2 (