The Archean atmosphere.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 32133393.
- Also identified by DOI 10.1126/sciadv.aax1420 and PMC identifier 7043912.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The atmosphere of the Archean eon-one-third of Earth's history-is important for understanding the evolution of our planet and Earth-like exoplanets. New geological proxies combined with models constrain atmospheric composition. They imply surface O<sub>2</sub> levels <10<sup>-6</sup> times present, N<sub>2</sub> levels that were similar to today or possibly a few times lower, and CO<sub>2</sub> and CH<sub>4</sub> levels ranging ~10 to 2500 and 10<sup>2</sup> to 10<sup>4</sup> times modern amounts, respectively. The greenhouse gas concentrations were sufficient to offset a fainter Sun. Climate moderation by the carbon cycle suggests average surface temperatures between 0° and 40°C, consistent with occasional glaciations. Isotopic mass fractionation of atmospheric xenon through the Archean until atmospheric oxygenation is best explained by drag of xenon ions by hydrogen escaping rapidly into space. These data imply that substantial loss of hydrogen oxidized the Earth. Despite these advances, detailed understanding of the coevolving solid Earth, biosphere, and atmosphere remains elusive, however.