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Proceedings Paper

Evidence of ancient microbial activity on Mars
Author(s): Jamie Wallis; N. C. Wickramasinghe; Daryl H. Wallis; Nori Miyake; M. K. Wallis; Richard B. Hoover
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Paper 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.

Paper Details

Date Published: 25 September 2015
PDF: 13 pages
Proc. SPIE 9606, Instruments, Methods, and Missions for Astrobiology XVII, 96060V (25 September 2015); doi: 10.1117/12.2186518
Show Author Affiliations
Jamie Wallis, Cardiff Univ. (United Kingdom)
N. C. Wickramasinghe, The Univ. of Buckingham (United Kingdom)
Daryl H. Wallis, The Univ. of Buckingham (United Kingdom)
Nori Miyake, The Univ. of Buckingham (United Kingdom)
M. K. Wallis, The Univ. of Buckingham (United Kingdom)
Richard B. Hoover, The Univ. of Buckingham (United Kingdom)
Athens State Univ. (United States)

Published in SPIE Proceedings Vol. 9606:
Instruments, Methods, and Missions for Astrobiology XVII
Richard B. Hoover; Gilbert V. Levin; Alexei Yu. Rozanov; Nalin C. Wickramasinghe, Editor(s)

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