DOI: 10.1073/pnas.1910698117
论文题名: Oxidized micrometeorites suggest either high pCO2 or low pN2 during the Neoarchean
作者: Payne R.C. ; Brownlee D. ; Kasting J.F.
刊名: Proceedings of the National Academy of Sciences of the United States of America
ISSN: 0027-8424
出版年: 2020
卷: 117, 期: 3 起始页码: 1360
结束页码: 1366
语种: 英语
英文关键词: Archean
; Atmospheric CO2
; Climate
; Micrometeorites
Scopus关键词: carbon dioxide
; iron
; iron micrometeorite
; methane
; nitrogen
; oxidizing agent
; oxygen
; unclassified drug
; Article
; atmosphere
; concentration (parameter)
; glaciation
; greenhouse gas
; Neoarchean
; oxidation
; partial pressure
; photochemistry
; priority journal
; temperature
; warming
英文摘要: Tomkins et al. [A. G. Tomkins et al., Nature 533, 235-238 (2016)] suggested that iron oxides contained in 2.7-Ga iron micrometeorites can be used to determine the concentration of O2 in the Archean upper atmosphere. Specifically, they argued that the presence of magnetite in these objects implies that O2 must have been near present-day levels (∼21%) within the altitude range where the micrometeorites were melted during entry. Here, we reevaluate their data using a 1D photochemical model. We find that atomic oxygen, O, is the most abundant strong oxidant in the upper atmosphere, rather than O2. But data from shock tube experiments suggest that CO2 itself may also serve as the oxidant, in which case micrometeorite oxidation really constrains the CO2/N2 ratio, not the total oxidant abundance. For an atmosphere containing 0.8 bar of N2, like today, the lower limit on the CO2 mixing ratio is ∼0.23. This would produce a mean surface temperature of ∼300 K at 2.7 Ga, which may be too high, given evidence for glaciation at roughly this time. If pN2was half the present value, andwarming by other greenhouse gases like methane was not a major factor, the mean surface temperature would drop to ∼291 K, consistent with glaciation. This suggests that surface pressure in the Neoarchean may need to have been lower-closer to 0.6 bar-for CO2 to have oxidized the micrometeorites. Ultimately, iron micrometeorites may be an indicator for ancient atmospheric CO2 and surface pressure; and could help resolve discrepancies between climate models and existing CO2 proxies such as paleosols. © 2020 National Academy of Sciences. All rights reserved. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/164358
Appears in Collections: 气候变化与战略
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作者单位: Payne, R.C., Department of Geosciences, Pennsylvania State University, University Park, PA 16802, United States; Brownlee, D., Department of Astronomy, University of Washington, Seattle, WA 98195, United States; Kasting, J.F., Department of Geosciences, Pennsylvania State University, University Park, PA 16802, United States
Recommended Citation:
Payne R.C.,Brownlee D.,Kasting J.F.. Oxidized micrometeorites suggest either high pCO2 or low pN2 during the Neoarchean[J]. Proceedings of the National Academy of Sciences of the United States of America,2020-01-01,117(3)