Oxidative Alteration of Ferrous Smectites: A Formation Pathway for Martian Nontronite?

Ferric (Fe3+-bearing) smectites, including nontronite, constitute the majority of hydrous mineral exposures observed on Mars. These smectite exposures are commonly interpreted as weathering products of Martian basaltic crust. However, ferrous (Fe2+-dominated) smectites, not ferric, are the thermo-dy...

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Published inNASA Center for AeroSpace Information (CASI). Conference Proceedings
Main Authors Chemtob, S M, Catalano, J G, Nickerson, R D, Morris, R V, Agresti, D G, Rivera-Banuchi, V, Liu, W, Yee, N
Format Conference Proceeding
LanguageEnglish
Published Hampton NASA/Langley Research Center 20.03.2017
Subjects
Evolution
Exposure
Mars
Mars surface
Organic chemistry
Oxidation
Oxidizing agents
Planetary geology
Smectites
Weathering
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Summary:Ferric (Fe3+-bearing) smectites, including nontronite, constitute the majority of hydrous mineral exposures observed on Mars. These smectite exposures are commonly interpreted as weathering products of Martian basaltic crust. However, ferrous (Fe2+-dominated) smectites, not ferric, are the thermo-dynamically predicted products of weathering in anoxic conditions, as predicted for early Mars. Earth was anoxic until the Proterozoic Great Oxidation Event; Mars likely experienced an analogous oxidative evolution to its present oxidized state, but the timing of this evolution is unresolved. We hypothesize that Fe3+-smectites observed by orbital spectroscopy are not the initial products of Noachian-era chemical weathering, but are instead the oxidative products of primary Fe2+-smectites. To test this hypothesis experimentally, we synthesized ferrous smectites and exposed them to Mars-relevant oxidants.