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Photochemistry of methane in the earth's early atmosphereThe photochemical behavior of methane in the early terrestrial atmosphere is investigated with a detailed model in order to determine how much CH4 might have been present and what types of higher hydroocarbons could have been formed. It is found that any primordial methane accumulated during the course of earth accretion would have been dissipated by photochemical reactions in the atmosphere in a geologically short period of time after the segregation of the core. Abiotic sources of methane are not likely to have been large enough to sustain CH4 mixing ratios as high as 10 to the -6th, the threshold for a possible methane greenhouse, with a CO-rich atmosphere being a possible exception. After the origin of life an increasing biogenic source of methane may have driven CH4 mixing ratios well above 10 to the 6th. The rise of atmospheric oxygen in the early Proterozoic may have led to a more rapid photochemical destruction of methane, lowering the mixing ratio to its present value.
Document ID
19840029263
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Kasting, J. F.
(NASA Ames Research Center Moffett Field, CA; National Center for Atmospheric Research, Boulder, CO, United States)
Zahnle, K J.
(NASA Ames Research Center Moffett Field, CA, United States)
Walker, J. C. G.
(Michigan, University Ann Arbor, MI, United States)
Date Acquired
August 12, 2013
Publication Date
January 1, 1983
Publication Information
Publication: Precambrian Research
Volume: 20
ISSN: 0301-9268
Subject Category
Geophysics
Accession Number
84A12050
Funding Number(s)
CONTRACT_GRANT: NAGW-176
Distribution Limits
Public
Copyright
Other

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