Biology
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.p43c1449v&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #P43C-1449
Biology
[0463] Biogeosciences / Microbe/Mineral Interactions, [5200] Planetary Sciences: Astrobiology, [5220] Planetary Sciences: Astrobiology / Hydrothermal Systems And Weathering On Other Planets
Scientific paper
We report on the mineralogy, organic preservation potential and habitability of sulfate deposits in acid sulfate volcanic settings at Valles Caldera, New Mexico. Fumaroles and acidic springs are potential analogs for aqueous environments on Mars and may offer insights into habitability of sulfate deposits such as those at Meridiani Planum. Sulfates recently detected on Mars are posited to have formed from fluids derived from basaltic weathering and igneous volatile input, ultimately precipitating from acidic brines subjected to desiccation and freeze-thaw cycles (McClennan and Grotzinger, 2008). Key issues concerning martian sulfate deposits are their relationship to aqueous clay deposits, and whether or not specific sulfates deposits represent former habitable environments (see Soderblum and Bell, 2008; Tosca et al., 2008). Modern terrestrial volcanic fumaroles and hot springs precipitate various Ca-, Mg- and Fe- sulfates along with clays, and can help clarify whether certain acid sulfate mineral assemblages reflect habitable environments. Valles caldera is a resurgent caldera last active in the Pleistocene (1.4 - 1.0 Ma) that hosts several active fumaroles and over 40 geothermal exploration wells (see Goff, 2009). Fumaroles and associated mudpots and springs at Valles range from pH < 1 to 3, and affect argillic alteration upon rhylolitic tuffs and sedimentary deposits (Charles et al., 1986). We identified assemblages containing gypsum, quartz, Al-sulfates, elemental sulfur, clays and other minerals using XRD and SEM-EDS. Our previous research has shown that sulfates from different marine depositional environments display textural and morphological traits that are indicative of biological influence, or specific conditions in the depositional environments (Vogel et al., 2009). Gypsum crystals that develop in the presence of microbial biofilms in marine environments may have distorted crystal morphologies, biofilm - associated dissolution features, and accessory carbonate minerals. Gypsum from Valles Caldera fumaroles develops in the absence of microbial biofilms and differs from biologically influenced marine gypsum in terms of is highly prismatic morphology, lack of texture, and association with clays, and other sulfates. Studies of Valles gypsum crystals therefore support the uniqueness of the putative morphological biosignatures in marine gypsum. We also assayed organic matter from fumarole encrustations to understand how low pH and sulfate content may discriminate against or enhance preservation of specific classes of organic compounds in acid sulfate environments. Similar to gypsiferous marine environments, organics are characterized by abundant organosulfur complexes. Long chain alkanes (> nC22) are abundant from acid sulfate environments. As with hypersaline marine depositional environments, sulfidation appears to be a major diagenetic pathway for organic matter in acid sulfate environments.
Des Marais David J.
Jahnke Lukas
Kubo Masahito
Vogel Marilyn B.
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