Origins 2011 – Abstracts
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O3b: Contributed Orals – Early Earth processes (continued)
Enrichment of Mo in the 3.2 Ga old Black Shales Recovered by DXCL-DP (Dixon Island-Cleaverville Drilling Project) in Pilbara, Western Australia
1Toho University, Japan; 2NASA Astrobiology Institute; 3Kyushu Univ., Japan; 4Kochi Univ., Japan; 5NIPR, Japan; 6Ibaraki Univ., Japan
We analyzed total chemical compositions of 96 black shale samples from drillcore DX, CL1, and CL2. all belong to the 3.2 Ga Dixon Island Fm. A combined enrichment of Mo, Corg, and S, together with enriched S isotopic compositions for a sedimentary formation may be used as a strong evidence for operation of modern-day style sedimentary Mo enrichment, implying that oxygenation of the atmosphere and oceans was significant during deposition of the sediments, ~800 Ma earlier than commonly thought.
Modeling free energy availability from Hadean Hydrothermal Vents to the first metabolism
1Max Planck Institut für Biogeochemie, Germany; 2JPL, California Institute of Technology, Pasadena, USA
Hadean ocean is considered, in its acid condition. Off-Axis Hydrothermal Vents transfer energy in the form of heat from the Earth’s interior to its surface, adding chemical free energy (as reduced compounds). We show that non-equilibrium thermodynamics helps in elucidating the limits of available free energy generated from a geothermal heat flux to provide conditions for the emergence of metabolism.
Primordial Ocean Chemistry and its Compatibility with the RNA World
1Scripps Institution of Oceanography, UCSD, United States of America; 2Department of Chemistry & Biochemistry, University of San Diego, United States of America
At pH 7 and 25°, decomposition half-lives of ribose and cytosine are ~200 days and ~250 years and that for phosphodiester bond hydrolysis ~25 years. The early ocean pH was likely lower from elevated levels of CO2. At 25°C and CO2 = 0.1-10 atm, pH would have been ~6 to ~4.7. At these pHs and 25°C ribose stability increases to 430 and 7600 years while the rates for the other reactions are little changed. Lower pHs could cause changes in RNA folding and thus impair RNA catalytic functions.