Anders JohansenUniversity of Copenhagen, Eloi CamprubiUniversity of Texas Rio Grande Valley, Elishevah van KootenUniversity of Copenhagen, Jens HoeijmakersLund University
{"title":"Self-oxidation of the atmospheres of rocky planets with implications for the origin of life","authors":"Anders JohansenUniversity of Copenhagen, Eloi CamprubiUniversity of Texas Rio Grande Valley, Elishevah van KootenUniversity of Copenhagen, Jens HoeijmakersLund University","doi":"arxiv-2409.11070","DOIUrl":null,"url":null,"abstract":"Rocky planets may acquire a primordial atmosphere by outgassing of volatiles\nfrom their magma ocean. The distribution of O between H$_2$O, CO and CO$_2$ in\nchemical equilibrium subsequently changes significantly with decreasing\ntemperature. We explore here two chemical models: one where CH$_4$ and NH$_3$\nare assumed to be irrevocably destroyed by photolysis, and one where these\nmolecules persist. In the first case, we show that CO cannot co-exist with\nH$_2$O, since CO oxidizes at low temperatures to form CO$_2$ and H$_2$. In both\ncases, H escapes from the thermosphere within a few ten million years by\nabsorption of stellar XUV radiation. This escape drives an atmospheric\nself-oxidation process whereby rocky planet atmospheres become dominated by\nCO$_2$ and H$_2$O, regardless of their initial oxidation state at outgassing.\nHCN is considered a potential precursor of prebiotic compounds and RNA. Our\noxidizing atmospheres are inefficient at producing HCN by lightning. Instead,\nwe demonstrate that lightning-produced NO, which dissolves as nitrate in the\noceans, and interplanetary dust particles may be the main sources of fixed\nnitrogen to emerging biospheres. Our results highlight the need for\norigin-of-life scenarios where the first metabolism fixes its C from CO$_2$,\nrather than from HCN and CO.","PeriodicalId":501209,"journal":{"name":"arXiv - PHYS - Earth and Planetary Astrophysics","volume":"26 1","pages":""},"PeriodicalIF":0.0000,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"arXiv - PHYS - Earth and Planetary Astrophysics","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/arxiv-2409.11070","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
Abstract
Rocky planets may acquire a primordial atmosphere by outgassing of volatiles
from their magma ocean. The distribution of O between H$_2$O, CO and CO$_2$ in
chemical equilibrium subsequently changes significantly with decreasing
temperature. We explore here two chemical models: one where CH$_4$ and NH$_3$
are assumed to be irrevocably destroyed by photolysis, and one where these
molecules persist. In the first case, we show that CO cannot co-exist with
H$_2$O, since CO oxidizes at low temperatures to form CO$_2$ and H$_2$. In both
cases, H escapes from the thermosphere within a few ten million years by
absorption of stellar XUV radiation. This escape drives an atmospheric
self-oxidation process whereby rocky planet atmospheres become dominated by
CO$_2$ and H$_2$O, regardless of their initial oxidation state at outgassing.
HCN is considered a potential precursor of prebiotic compounds and RNA. Our
oxidizing atmospheres are inefficient at producing HCN by lightning. Instead,
we demonstrate that lightning-produced NO, which dissolves as nitrate in the
oceans, and interplanetary dust particles may be the main sources of fixed
nitrogen to emerging biospheres. Our results highlight the need for
origin-of-life scenarios where the first metabolism fixes its C from CO$_2$,
rather than from HCN and CO.