Reflectance spectra of solid organic acids and their mixtures with Fe-sulfide pyrrhotite: Insights into the surface composition of comet 67P/CG

Abstract

We present 0.3-17 µm reflectance spectra of different solid organic acids (including amino acids) and their fine-grained intimate mixtures with pyrrhotite (Fe1-xS), a Fe-sulfide. These data provide a valuable basis for compositional interpretation of remote sensing spectra of the comet 67P/CG’s surface. In particular, we investigate the ability of an opaque Fe-sulfide to suppress absorption bands of organic acids and to modify key spectral parameters such as contrasts, widths, shapes of absorption bands and continuum slopes. Finally, we compare our results to the VIRTIS/Rosetta spectra of comet 67P surface in order to assess the possible contribution of carboxylic O-H vibrations to the broad complex 3.2-µm absorption band in the comet spectra.