Rethinking early Earth phosphorus geochemistry
- National Aeronautics and Space Administration (NASA) Astrobiology Institute (NAI) LaPlace Center, University of Arizona, 1629 East University Boulevard, Tucson, AZ 85719
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Edited by Donald E. Canfield, University of Southern Denmark, Odense M, Denmark, and approved December 6, 2007 (received for review August 29, 2007)
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Fig. 1.Structures of biological P molecules at pH 8. (Left) Inorganic P molecules are shown. (Right) Representative organic P molecules are shown.
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Fig. 2.Thermodynamic stability diagrams for P species. (A) Eh-pH diagram for P species at 298 K, 10−6 M, with dashed lines representing the present-day atmosphere (Upper) and lower limit on water stability (Lower). (B) Condensation sequence for P minerals assuming 10−4 bar and solar elemental abundances.
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Fig. 3.NMR spectrum of Fe2+, H2O2, and HPO3 2− in solution after 1 day. From left to right, the peaks are orthophosphate (6.5 ppm), phosphite (4 ppm), pyrophosphate (−4 ppm), and triphosphate (small peak at −17.5 ppm).
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Fig. 4.Oxidative half-life for 1 mM solution of phosphite (HPO3 2−) vs. atmospheric H2 content. The top profile is based on the estimate of UV flux under a CO2-rich atmosphere, whereas the bottom profile assumes no CO2 (70).
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Fig. 5.Eh-pH diagram for radical aqueous P species, 10−6 M, with dashed lines representing the present-day atmosphere (Upper) and lower limit on water stability (Lower).
Footnotes
- *To whom correspondence should be addressed. E-mail: mpasek{at}lpl.arizona.edu
- © 2008 by The National Academy of Sciences of the USA
