Mineralogic constraints on sulfur-rich soils from Pancam spectra at Gusev crater, Mars

[1] The Mars Exploration Rover (MER) Spirit excavated sulfur-rich soils exhibiting high albedo and relatively white to yellow colors at three main locations on and south of Husband Hill in Gusev crater, Mars. The multispectral visible/near-infrared properties of these disturbed soils revealed by the Pancam stereo color camera vary appreciably over small spatial scales, but exhibit spectral features suggestive of ferric sulfates. Spectral mixture models constrain the mineralogy of these soils to include ferric sulfates in various states of hydration, such as ferricopiapite [Fe2/32+Fe43+(SO4)(6)(OH)(2) center dot 20(H2O)], hydronium jarosite [(H3O)Fe-3(3+) (SO4)(2)(OH)(6)], fibroferrite [Fe3+(SO4)(OH) center dot 5(H2O)], rhomboclase [HFe3+(SO4)(2) center dot 4(H2O)], and paracoquimbite [Fe-2(3+) (SO4)(3) center dot 9(H2O)].