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Bolide impacts and the oxidation state of carbon in the earth's early atmosphereA one-dimensional photochemical model was used to examine the effect of bolide impacts on the oxidation state of earth's primitive atmosphere. The impact rate should have been high prior to 3.8 Ga before present, based on evidence derived from the moon. Impacts of comets or carbonaceous asteroids should have enhanced the atmospheric CO/CO2 ratio by bringing in CO ice and/or organic carbon that can be oxidized to CO in the impact plume. Ordinary chondritic impactors would contain elemental iron that could have reacted with ambient CO2 to give CO. Nitric oxide (NO) should also have been produced by reaction between ambient CO2 and N2 in the hot impact plumes. High NO concentrations increase the atmospheric CO/CO2 ratio by increasing the rainout rate of oxidized gases. According to the model, atmospheric CO/CO2 ratios of unity or greater are possible during the first several hundred million years of earth's history, provided that dissolved CO was not rapidly oxidized to bicarbonate in the ocean.
Document ID
19910034314
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Kasting, James F.
(Pennsylvania State University University Park, United States)
Date Acquired
August 15, 2013
Publication Date
January 1, 1990
Publication Information
Publication: Origins of Life and Evolution of the Biosphere
Volume: 20
Issue: 4-Mar
ISSN: 0169-6149
Subject Category
Geophysics
Accession Number
91A18937
Funding Number(s)
CONTRACT_GRANT: NSF ATM-89-01775
CONTRACT_GRANT: NCA2-369
Distribution Limits
Public
Copyright
Other

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