Evidence of ancient microbial activity on Mars

Jamie Wallis; N. C. Wickramasinghe; Daryl H. Wallis; Nori Miyake; M. K. Wallis; Richard B. Hoover

doi:10.1117/12.2186518

25 September 2015 Evidence of ancient microbial activity on Mars

Jamie Wallis, N. C. Wickramasinghe, Daryl H. Wallis, Nori Miyake, M. K. Wallis, Richard B. Hoover

Proceedings Volume 9606, Instruments, Methods, and Missions for Astrobiology XVII; 96060V (2015) https://doi.org/10.1117/12.2186518
Event: SPIE Optical Engineering + Applications, 2015, San Diego, California, United States

Abstract

We report for the first time in situ observations of a relatively rare secondary iron arsenate-sulphate mineral named bukovskýite – Fe³⁺ ₂(As⁵⁺O₄)(S⁶⁺O₄)(OH)•7(H₂O) - found in a shock melt vein of the Tissint Martian meteorite. It is hypothesised that the mineral formed when high concentrations of aqueous H⁺, Fe(III), SO₄ and AsO₄ were maintained for long periods of time in microenvironments created within wet subsurface Martian clays. The aqueous H⁺, Fe(III), SO₄ and AsO₄ species arose from the microbial oxidation of FeS₂ with concurrent release of sequestrated As. The availability of aqueous AsO₄ would also be complemented by dissolution by-products of the microbial reduction of Feoxides influenced by dissolved organic matter that alters the redox state and the complexation of As, thus shifting As partitioning in favour of the solute phase. This hypothesis is substantially supported by SEM analysis of a 15μm spherical structure comprising of a carbonaceous outer coating with a inner core of FeS₂ (pyrite) that showed the pyrite surface with spherical pits, and chains of pits, with morphologies distinct from abiotic alteration features. The pits and channels have a clustered, geometric distribution, typical of microbial activity, and are closely comparable to biologically mediated microstructures created by Fe- and S-oxidising microbes in the laboratory. These microstructures are interpreted as trace fossils resulting from the attachment of bacteria to the pyrite surfaces.

Citation Download Citation

Jamie Wallis, N. C. Wickramasinghe, Daryl H. Wallis, Nori Miyake, M. K. Wallis, and Richard B. Hoover "Evidence of ancient microbial activity on Mars", Proc. SPIE 9606, Instruments, Methods, and Missions for Astrobiology XVII, 96060V (25 September 2015); https://doi.org/10.1117/12.2186518

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