Catling David C, Zahnle Kevin J
Department of Earth and Space Sciences and cross-campus Astrobiology Program, Box 351310, University of Washington, Seattle, WA 98195, USA.
Space Sciences Division, NASA Ames Research Center, MS 245-3, Moffett Field, CA 94035, USA.
Sci Adv. 2020 Feb 26;6(9):eaax1420. doi: 10.1126/sciadv.aax1420. eCollection 2020 Feb.
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 levels <10 times present, N levels that were similar to today or possibly a few times lower, and CO and CH levels ranging ~10 to 2500 and 10 to 10 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.
太古宙（约占地球历史的三分之一）的大气对于理解我们这颗行星以及类地系外行星的演化至关重要。新的地质代理指标与模型相结合，限制了大气成分。这些指标表明，当时地表的氧气水平低于现今的10倍，氮气水平与现今相似，或者可能比现今低几倍，一氧化碳和甲烷水平分别约为现代含量的10至2500倍和10至10倍。温室气体浓度足以抵消太阳较弱时的影响。碳循环对气候的调节作用表明，当时地表平均温度在0°C至40°C之间，这与偶尔出现的冰川作用相符。从太古宙到大气氧化阶段，大气氙的同位素质量分馏现象，最好的解释是氢迅速逃逸到太空时氙离子受到拖拽。这些数据表明，大量的氢流失使地球发生了氧化。然而，尽管取得了这些进展，对于地球固体、生物圈和大气共同演化的详细理解仍然难以捉摸。
