Oxidised micrometeorites as evidence for low atmospheric pressure on the early Earth

Rimmer, P. B. and Shorttle, Oliver and Rugheimer, S. (2019) Oxidised micrometeorites as evidence for low atmospheric pressure on the early Earth. Geochemical Perspectives Letters, 9. pp. 38-42. ISSN 2410-3403 DOI https://doi.org/10.7185/geochemlet.1903

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Abstract

Reconstructing a record of the partial pressure of molecular oxygen in Earth’s atmosphere is key for understanding macroevolutionary and environmental change over geological history. Recently, the oxidation state of iron in micrometeorites has been taken to imply the presence of modern Earth concentrations of oxygen in the upper atmosphere at 2.7 Ga, and therefore a highly chemically stratified atmosphere (Tomkins et al., 2016). We here explore the possibility that the mixing ratio of oxygen in Earth’s upper atmosphere, that probed by micrometeorites, may instead be sensitive to the surface atmospheric pressure. We find that the concentrations of oxygen in the upper atmosphere required for micrometeorite oxidation are achieved for a 0.3 bar atmosphere. In this case, significant water vapour reaches high up in the atmosphere and is photodissociated, leading to the formation of molecular oxygen. The presence of oxidised iron in micrometeorites at 2.7 Ga may therefore be further evidence that the atmospheric pressure at the surface of the early Earth was substantially lower than it is today.

Item Type: Article
Uncontrolled Keywords: 2018AREP; IA74
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
05 - Petrology - Igneous, Metamorphic and Volcanic Studies
07 - Gold Open Access
Journal or Publication Title: Geochemical Perspectives Letters
Volume: 9
Page Range: pp. 38-42
Identification Number: https://doi.org/10.7185/geochemlet.1903
Depositing User: Sarah Humbert
Date Deposited: 14 Feb 2019 18:26
Last Modified: 14 Feb 2019 18:26
URI: http://eprints.esc.cam.ac.uk/id/eprint/4423

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