Mathematics – Logic
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufm.p13b1379m&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #P13B-1379
Mathematics
Logic
[6225] Planetary Sciences: Solar System Objects / Mars
Scientific paper
Traditional analysis of evaporite environments have either focused on the geology or the halophilic organisms. It is relatively rare that the two have been combined and even rarer that both disciplines have been incorporated in comparing evaporite sites. The variation in evaporite environments does influence microbial ecology and fossilization processes as each site varies in pH, temperature, presence or absence springs, and spring chemistry. Understanding the evaporite environments is important for planetary scientists as they serve as analogs for evaluating extraterrestrial materials, including the potential for water and ultimately life. For example Mars lander, rover and orbital missions have identified the evaporite signatures of gypsum, carbonates and chlorides, all indicating that water existed at sometime in the planets geological history. Terrestrial evaporite sites all possess halophilic tolerant life. In some instances such as the Dead Sea, Israel, it is restricted to microbial life, but in other sites there are higher life forms. The microbes associated with these evaporite sites can produce biofilms as a method to develop their own microenvironments. Microorganisms can be observed colonizing specific ecological niches or gradients can be created by these environments. These gradients occur due the localized drying and weathering patterns that create different soil chemistry. The microorganisms in turn colonize specific areas more suitable to their specific metabolic needs. For example, under anaerobic conditions with sulfur and methane prevalent methanogenic and/or sulfur reducing microbial species may be observed. However, under similar chemistry environments with the exception of aerobic conditions sulfur oxidizer and/or methanotrophic microorganism may occur. Because of their conspicuous colored pigments purple sulfur bacteria are frequently observed in anoxic zones of lakes, sulfur springs, and stratified evaporite crusts. Some of these bacteria are of particular interest including Ectothiorhodospira spp. that deposit extracellular sulfur and are halophilic growing at high pH with NaCl concentrations approaching saturation. Fossilization and biofilm production appears to be relevant to the geochemistry of the systems. For example Dead Sea, Israel, microbes produce minimal biofilms, reside in the sediments, and the incidence of fossilization is low while hypersaline Storrs Lake, San Salvador, Bahamas microbes produce prodigious amounts of biofilms with many examples of fossilization. Some of the microbes appear to prefer solid substrates and may exhibit a preference, such as detrital or mineral, etc. In our studies we have found that some of the organisms, in relation to their substrate, can be tentatively characterized with laser confocal scanning microscopy. Terrestrial evaporite sites and understanding potential biomarkers and/or mineral signatures are important for identifying potential exoplanetary sites such as Mars that may harbor life.
Brigmon R. L.
Morris Alan P.
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