Biogenic methane, hydrogen escape, and the irreversible oxidation of early Earth (2001)
| Venue: | Science |
| Citations: | 32 - 1 self |
BibTeX
@ARTICLE{Catling01biogenicmethane,,
author = {David C. Catling and Kevin J. Zahnle and Christopher P. Mckay},
title = {Biogenic methane, hydrogen escape, and the irreversible oxidation of early Earth},
journal = {Science},
year = {2001},
pages = {839--843}
}
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Abstract
The low O2 content of the Archean atmosphere implies that methane should have been present at levels;102 to 103 parts per million volume (ppmv) (compared with 1.7 ppmv today) given a plausible biogenic source. CH4 is favored as the greenhouse gas that countered the lower luminosity of the early Sun. But abundant CH4 implies that hydrogen escapes to space (1space) orders of magnitude faster than today. Such reductant loss oxidizes the Earth. Pho-tosynthesis splits water into O2 and H, and methanogenesis transfers the H into CH4. Hydrogen escape after CH4 photolysis, therefore, causes a net gain of oxygen [CO2 1 2H2O3 CH4 1 2O23 CO2 1 O2 1 4H(1space)]. Expected irreversible oxidation (;1012 to 1013 moles oxygen per year) may help explain how EarthÕs surface environment became irreversibly oxidized. The rise of atmospheric O2 about 2.4 to 2.2 billion years ago (Ga) (1, 2) changed the course of biological evolution. Yet explain-ing why O2 rose at that time has remained
Keyphrases
irreversible oxidation hydrogen escape biogenic methane early earth atmospheric o2 pho-tosynthesis split water biological evolution oxygen co2 reductant loss ppmv today greenhouse gas plausible biogenic source ch4 photolysis net gain earth surface environment methanogenesis transfer early sun abundant ch4 implies archean atmosphere implies low o2 content
