Comparative Spectroscopic Study of Three Ferric Sulfates: Kornelite, Lausenite

Introduction: Sulfates have been identified on Mars by orbital remote sensing (OMEGA and CRISM) and during surface exploration (Viking, MER) [1-4]. MER rovers have found Fe-sulfates at both landing sites. A ferric sulfate (jarosite) was identified with the Mössbauer spectrometer (MB) in Meridiani Planum outcrops (~10 wt.%) [5]. At Gusev Crater, light-toned salty soils are hydrous as seen by MiniTES[6], and could contain ferricopiapite, hydronium jarosite, fibroferrite, rhomboclase and paracoquimbite based on a Pancam spectral analysis [7]. To uncover the mysteries related to hydrologic stories of ferric sulfates on Mars, we have conducted a systematic spectroscopic study on hydrated ferric sulfates [8]. We prepared seven ferric sulfates from pure chemicals, confirmed their structures by XRD, and obtained their characteristic Raman spectra, which make the basis for non-invesive Raman identification in the study of stability studies and phase transition pathways under Mars-relevant environmental conditions, and will also be used during Raman-LIBS investigation on ESA’s ExoMars mission.In this abstract, we report a set of Raman and Vis-NIR spectroscopic study on three hydrated ferric sulfates, kornelite (Fe2(SO4)3·7H2O), lausenite (Fe2(SO4)3.6H2O), and pentahydrate (Fe2(SO4)3·5H2O).