Document Detail

Abiotic nitrogen reduction on the early Earth.
MedLine Citation:
PMID:  9759725     Owner:  NLM     Status:  MEDLINE    
The production of organic precursors to life depends critically on the form of the reactants. In particular, an environment dominated by N2 is far less efficient in synthesizing nitrogen-bearing organics than a reducing environment rich in ammonia. Relatively reducing lithospheric conditions on the early Earth have been presumed to favour the generation of an ammonia-rich atmosphere, but this hypothesis has not been studied experimentally. Here we demonstrate mineral-catalysed reduction of N2, NO2- and NO3- to ammonia at temperatures between 300 and 800 degrees C and pressures of 0.1-0.4 GPa-conditions typical of crustal and oceanic hydrothermal systems. We also show that only N2 is stable above 800 degrees C, thus precluding significant atmospheric ammonia formation during hot accretion. We conclude that mineral-catalysed N2 reduction might have provided a significant source of ammonia to the Hadean ocean. These results also suggest that, whereas nitrogen in the Earth's early atmosphere was present predominantly as N2, exchange with oceanic, hydrothermally derived ammonia could have provided a significant amount of the atmospheric ammonia necessary to resolve the early-faint-Sun paradox.
J A Brandes; N Z Boctor; G D Cody; B A Cooper; R M Hazen; H S Yoder
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Nature     Volume:  395     ISSN:  0028-0836     ISO Abbreviation:  Nature     Publication Date:  1998 Sep 
Date Detail:
Created Date:  1998-10-19     Completed Date:  1998-10-19     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0410462     Medline TA:  Nature     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  365-7     Citation Subset:  IM; S    
Geophysical Laboratory, Carnegie Institution of Washington, DC 20015-1305, USA.
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MeSH Terms
Ammonia / chemistry
Earth (Planet)
Evolution, Planetary
Iron / chemistry
Nitrogen / chemistry*
Reg. No./Substance:
7439-89-6/Iron; 7664-41-7/Ammonia; 7727-37-9/Nitrogen
Comment In:
Nature. 1998 Sep 24;395(6700):329-30   [PMID:  9759720 ]

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