"Could a photosynthetic plant survive on Mars using the Sun's energy to perform photosynthesis?"
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Methanogenesis in Hypersaline Environments: The Use of Carbon and Hydrogen Isotopic Signatures to Evaluate the Biogenicity of Methane in a Mars Analogue Environment and on Mars
PI: Bebout, Brad
The recent reports of hypersaline paleo-environments on Mars, as well as measurements of methane in that planet’s atmosphere, have underscored the need to evaluate the importance of biological (as opposed to geological) trace gas production and consumption. Modern hypersaline microbial mat communities, (thought to be analogous to those present on the early Earth at a period of time when Mars was experiencing very similar environmental conditions), have been shown to produce methane. However, very little is known about the physical and/or biological controls imposed upon the rates at which methane, and other important trace gases, are produced and consumed in these environments. In studying methane production in the Guerrero Negro hypersaline ecosystem, Baja California Mexico, we have measured high concentrations of methane in bubbles of gas produced both in the sediments underlying microbial mats (including one site where methane constitutes over 20% by volume of the bubbles), as well as in areas not colonized by microbial mats. The carbon isotopic signature (del13C ratio) of the methane in the bubbles exhibited an extremely wide range of values, from ca. -75 per mil to ca. -25 per mil, potentially complicating interpretations of biogenicity. Further work is needed to understand the isotopic signature of released methane and the possible biological and chemical oxidation in these environments. The isotopic ratio of hydrogen in methane (the D/H ratio) in combination with the carbon isotopic signature, and concentrations of C1 to C3 gases generally produced by thermogenic methane formation are all necessary for an unequivocal determination of biogenicity of methane, including Martian methane, as was recently reviewed by Allen et al. (2006a, 2006b). The capability for del13C and D/H measurements will be present on Mars in the Mars Science Laboratory (MSL), and will be used to evaluate biogenicity. However, few measurements of this type have been made, even on Earth, and we are aware of no data from hypersaline environments.
We propose an intensive investigation of methanogenesis in hypersaline environments, including environments containing sulfate minerals similar to those reported on Mars. We will combine isotopic measurements of methane with measurements of its concentration and rates of production. We will identify methanogenic microorganisms, and pathways used to by them to produce and/or oxidize methane because these biogeochemical processes produce diagnostic isotopic signatures in methane that is released from these environments. This work will lead to a better understanding of the processes producing and consuming methane in Mars analogue environments and provide a framework within which MSL results, as well as results from other missions, such as Terrestrial Planet Finder, may be interpreted.
