Capacity of Chlorate to Oxidize Ferrous Iron: Implications for Iron Oxide Formation on Mars
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Department of Earth & Planetary Sciences, Washington University, St. Louis, MO 63130, USA
2
McDonnell Center for the Space Sciences, Washington University, St. Louis, MO 63130, USA
*
Author to whom correspondence should be addressed.
Minerals 2020, 10(9), 729; https://doi.org/10.3390/min10090729
Received: 20 July 2020
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Revised: 16 August 2020
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Accepted: 17 August 2020
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Published: 19 August 2020
(This article belongs to the Special Issue Expanding Views of Clays, Oxides, and Evaporites on Aquaplanets in the Solar System)
Chlorate is an important Cl-bearing species and a strong potential Fe(II) oxidant on Mars. Since the amount of oxychlorine species (perchlorate and chlorate) detected on Mars is limited (<~1 wt.%), the effectiveness of chlorate to produce iron oxides depends heavily on its oxidizing capacity. Decomposition of chlorate or intermediates produced during its reduction, before reaction with Fe(II) would decrease its effective capacity as an oxidant. We thus evaluated the capacity of chlorate to produce Fe(III) minerals in Mars-relevant fluids, via oxidation of dissolved Fe(II). Each chlorate ion can oxidize 6 Fe(II) ions under all conditions investigated. Mass balance demonstrated that 1 wt.% chlorate (as ClO3−) could produce approximately 6 to 12 wt.% Fe(III) or mixed valent mineral products, with the amount varying with the formula of the precipitating phase. The mineral products are primarily determined by the fluid type (chloride- or sulfate-rich), the solution pH, and the rate of Fe(II) oxidation. The pH at the time of initial mineral nucleation and the amount of residual dissolved Fe(II) in the system exert important additional controls on the final mineralogy. Subsequent diagenetic transformation of these phases would yield 5.7 wt.% hematite per wt.% of chlorate reacted, providing a quantitative constraint on the capacity of chlorate to generate iron oxides on Mars.
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Keywords:
Mars; oxychlorine; iron oxides; chlorate; oxidation
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MDPI and ACS Style
Mitra, K.; Moreland, E.L.; Catalano, J.G. Capacity of Chlorate to Oxidize Ferrous Iron: Implications for Iron Oxide Formation on Mars. Minerals 2020, 10, 729. https://doi.org/10.3390/min10090729
AMA Style
Mitra K, Moreland EL, Catalano JG. Capacity of Chlorate to Oxidize Ferrous Iron: Implications for Iron Oxide Formation on Mars. Minerals. 2020; 10(9):729. https://doi.org/10.3390/min10090729
Chicago/Turabian StyleMitra, Kaushik, Eleanor L. Moreland, and Jeffrey G. Catalano. 2020. "Capacity of Chlorate to Oxidize Ferrous Iron: Implications for Iron Oxide Formation on Mars" Minerals 10, no. 9: 729. https://doi.org/10.3390/min10090729
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