Nature | DeepDyve

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Kasting, James F.; Catling, David C.; Zahnle, Kevin

2012 Nature

Arising from F. Gaillard, B. Scaillet & N. T. Arndt Nature478, 229–232(2011)10.1038/nature10460Around 2.5 billion years ago, Earth’s atmosphere turned from anoxic to oxic in what is known as the Great Oxidation Event. Gaillard et al.1 suggest that this oxygenation was caused by the emergence of the continents and a shift in volcanism from predominantly submarine to primarily subaerial conditions. Because the ratio of volcanic SO2 to H2S in their model increases with this shift, they argue that the atmosphere became more oxidized. But their model also predicts that outgassing of CO2 decreases at the lower pressure of continental volcanism, and that this should act against atmospheric oxygenation because CO2 is the substrate for the production of oxygen from photosynthesis. Hence, their mechanism may not trigger a rise in atmospheric O2.

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Gaillard et al. reply

Gaillard, Fabrice; Scaillet, Bruno; Arndt, Nicholas T.

2012 Nature

doi: 10.1038/nature11275pmid: N/A

Replying to J. F. Kasting, D. C. Catling & K. Zahnle Nature487, 10.1038/nature11274 (2012)Kasting et al.1 question the model of ref. 2, in which we suggest that the oxygenation of the atmosphere, around 2.45 Gyr ago, was promoted by the emergence of subaerial volcanism, producing volcanic gases with much more elevated SO2/H2S ratios than submarine volcanism.

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LitStream Collection

Secret disservice

2012 Nature

doi: 10.1038/487405apmid: 22836961

Staff-surveillance efforts by government agencies must not contravene the rights of whistle-blowers, as the US Food and Drug Administration is accused of doing.

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LitStream Collection

Protect and serve

2012 Nature

doi: 10.1038/487405bpmid: 22836960