气候变化领域集成服务门户(CCPortal): Oxidized micrometeorites suggest either high pCO2 or low pN2 during the Neoarchean

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DOI	10.1073/pnas.1910698117
	Oxidized micrometeorites suggest either high pCO2 or low pN2 during the Neoarchean
	Payne R.C.; Brownlee D.; Kasting J.F.
发表日期	2020
ISSN	0027-8424
起始页码	1360
结束页码	1366
卷号	117 期号:3
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.
英文关键词	Archean; Atmospheric CO2; Climate; Micrometeorites
语种	英语
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
来源期刊	Proceedings of the National Academy of Sciences of the United States of America
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/161085
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
推荐引用方式 GB/T 7714	Payne R.C.,Brownlee D.,Kasting J.F.. Oxidized micrometeorites suggest either high pCO2 or low pN2 during the Neoarchean[J],2020,117(3).
APA	Payne R.C.,Brownlee D.,&Kasting J.F..(2020).Oxidized micrometeorites suggest either high pCO2 or low pN2 during the Neoarchean.Proceedings of the National Academy of Sciences of the United States of America,117(3).
MLA	Payne R.C.,et al."Oxidized micrometeorites suggest either high pCO2 or low pN2 during the Neoarchean".Proceedings of the National Academy of Sciences of the United States of America 117.3(2020).