Biology
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufm.p13b1393s&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #P13B-1393
Biology
[0406] Biogeosciences / Astrobiology And Extraterrestrial Materials, [0428] Biogeosciences / Carbon Cycling, [0448] Biogeosciences / Geomicrobiology, [0456] Biogeosciences / Life In Extreme Environments
Scientific paper
Serpentinization - a reaction between water and ultramafic rock (derived from the mantle) - is suspected to be a source of hydrocarbons such as methane on Mars. Through the hydration of ultramafic rock, this reaction produces hydrogen (H2) gas and reducing conditions necessary for abiogenic hydrocarbon synthesis, while also producing conditions amendable for the production of methane through microbial chemoautotrophic pathways. Mars analogue sites of present-day serpentinization can be used to determine what geochemical measurements are required for determining the reactions responsible for the methane in the Martian atmosphere. On Earth few locations that are known to exhibit active serpentinization are easily accessible. One such location is found in the Tablelands at Gros Morne National Park, Newfoundland. Peridotite rocks similar to those found on Mars dominate the Tablelands thus making the Tablelands an important analogue site for potential ecosystems on Mars. Present-day serpentinization is evidenced by fluid seeps characterized by highly alkaline (pH 11 to 12) and highly reducing (as low as -820 mV) conditions, travertine and the presence of dissolved methane. These fluids contain high concentrations of Ca2+ (~5.00x104ppb) compared to freshwater inputs (~ 1.00x103) and react at the surface with atmospheric CO2 producing travertine deposits (as CaCO3 precipitate). Dissolved H2 gas produced abiogenically through the serpentinization reaction also provides copious geofuels, which can be used for chemosynthesis. Preliminary data has shown that microbial life lives in the high pH springs of the Tablelands. Ongoing studies of targeted compounds including phospholipid fatty acids and ether-linked lipids are being used to determine the microbial community compositions and verify the occurrence of Bacteria and Archaea in these fluids. An important question is also the source of the serpentinized fluid seeps. Hydrogen (δ2H) and oxygen (δ18O) isotopes of these fluids indicate meteoric water. The site also receives freshwater inputs (pH 7) creating strong redox gradients with reducing seeps. Isotopic and geochemical analysis of the fluids, associated gases and carbonates, and preliminary results on microbial communities will be discussed to help understand how methane is produced in these springs at the Tablelands and how the information can be useful to help identify the source of methane on Mars.
Bower D. M.
Brazelton William J.
Morrill Penny L.
Schrenk Matthew O.
Steele Andrew
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