Biology
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.p43c1441b&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #P43C-1441
Biology
[0450] Biogeosciences / Hydrothermal Systems, [5215] Planetary Sciences: Astrobiology / Origin Of Life, [8135] Tectonophysics / Hydrothermal Systems, [8416] Volcanology / Mid-Oceanic Ridge Processes
Scientific paper
At the bottom of the terrestrial oceans, where tectonic forces separate the lithospheric plates along mid-ocean ridges, the ultramafic rocks of the upper-mantle, the peridotites, are exposed to circulating seawater and the hydrolysis of their silicate constituents, the olivine and pyroxenes minerals, into serpentine, occurs at various degrees. The H2, released during the serpentinization process, could react with the CO2 embedded inside the rock, to form methane and saturated hydrocarbons, in the context of catalytic reactions involving hydrothermal CO2. As a consequence, the simple molecules H2O, H2, CO2, CH4, could be present inside the rock and, with the N2 of the environment and an activation source, they could lead to simple organic molecules of biological relevance. Serpentinized peridotite rocks located on hydrothermal sites could consequently contain organic molecules, including amino acids. Some similarities with the Murchison meteorite can be noticed and are described. In order to verify this hypothesis, we conducted preliminary experimental analyses of the organic content of two serpentinized peridotite rocks of the Ashadze (12° 58'N, 4,080 m) and Logatchev (14° 43'N, 2,970 m) hydrothermal sites in the Mid-Atlantic Ridge. The samples have been dredged on the seafloor in march 2007, during the French-Russian Ifremer Serpentine cruise. Polar and non polar fractions of the grounded samples have been analysed by gas chromatoraphy/mass spectrometry techniques. We identify a wide variety of amino acids including protein and non-protein amino acids. Our analyses show that the identified amino acids are L-form predominent: for the Ashadze peridotite rock, for instance, the D/L ratio is 0.18. The results also show similarities with the values on D/L ratios found for sedimentary amino acids. We conclude in a biological origin for the identified amino acid peaks. However some peaks remain unidentified. We also detect long-chain n-alkane compounds (< n-C28H58) in the non-polar fraction under GC conditions up to 220°C. The GC/MS of the n-alkanes shows a decrease in intensity with increasing carbon number, which seems to be a characteristic of abiotic synthesis. However, we do not conclude yet in a biotic or abiotic origin for the identified n-alkanes. The analyses are described at: http://www.mdpi.com/1422-0067/10/7/2986/pdf
Bassez M.
Ohkouchi Nao
Takano Yasushi
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