Mössbauer mineralogy of rock, soil, and dust at Gusev crater, Mars: Spirit's journey through weakly altered olivine basalt on the plains and pervasively altered basalt in the Columbia Hills

Citation

Morris RV, Klingelhoefer G, Schröder C, Rodionov DS, Yen AS, Ming DW, de Souza Jr PA, Fleischer I, Wdowiak TJ, Gellert R, Bernhardt B, Evlanov EN, Zubkov BV, Foh J & Bonnes U (2006) Mössbauer mineralogy of rock, soil, and dust at Gusev crater, Mars: Spirit's journey through weakly altered olivine basalt on the plains and pervasively altered basalt in the Columbia Hills. Journal of Geophysical Research: Planets, 111 (E2), Art. No.: E02S13. https://doi.org/10.1029/2005JE002584

Abstract
The Mössbauer spectrometer on Spirit measured the oxidation state of Fe, identified Fe-bearing phases, and measured relative abundances of Fe among those phases for surface materials on the plains and in the Columbia Hills of Gusev crater. Eight Fe-bearing phases were identified: olivine, pyroxene, ilmenite, magnetite, nanophase ferric oxide (npOx), hematite, goethite, and a Fe3+-sulfate. Adirondack basaltic rocks on the plains are nearly unaltered (Fe3+/FeT < 0.2) with Fe from olivine, pyroxene (Ol > Px), and minor npOx and magnetite. Columbia Hills basaltic rocks are nearly unaltered (Peace and Backstay), moderately altered (WoolyPatch, Wishstone, and Keystone), and pervasively altered (e.g., Clovis, Uchben, Watchtower, Keel, and Paros with Fe3+/FeT ~ 0.6–0.9). Fe from pyroxene is greater than Fe from olivine (Ol sometimes absent), and Fe2+ from Ol + Px is 40–49% and 9–24% for moderately and pervasively altered materials, respectively. Ilmenite (Fe from Ilm 3–6%) is present in Backstay, Wishstone, Keystone, and related rocks along with magnetite (Fe from Mt 10–15%). Remaining Fe is present as npOx, hematite, and goethite in variable proportions. Clovis has the highest goethite content (Fe from Gt = 40%). Goethite (α-FeOOH) is mineralogical evidence for aqueous processes because it has structural hydroxide and is formed under aqueous conditions. Relatively unaltered basaltic soils (Fe3+/FeT ~ 0.3) occur throughout Gusev crater (60–80% Fe from Ol + Px, 10–30% from npOx, and 10% from Mt). PasoRobles soil in the Columbia Hills has a unique occurrence of high concentrations of Fe3+-sulfate (65% of Fe). Magnetite is identified as a strongly magnetic phase in Martian soil and dust.

Keywords
Mars; Mars Exploration Rovers; Mössbauer spectroscopy; weathering

Notes
Additional co-authors: E Kankeleit, P Gütlich, F Renz, SW Squyres, RE Arvidson

Journal
Journal of Geophysical Research: Planets: Volume 111, Issue E2

• MorrisJGR_02_06.pdf