The speciation of carbon, nitrogen, and water in magma oceans and its effect on volatile partitioning between major reservoirs of the Solar System rocky bodies

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dc.citation.firstpage281en_US
dc.citation.journalTitleGeochimica et Cosmochimica Actaen_US
dc.citation.lastpage301en_US
dc.citation.volumeNumber280en_US
dc.contributor.authorGrewal, Damanveer S.en_US
dc.contributor.authorDasgupta, Rajdeepen_US
dc.contributor.authorFarnell, Alexandraen_US
dc.date.accessioned2020-05-29T18:02:43Zen_US
dc.date.available2020-05-29T18:02:43Zen_US
dc.date.issued2020en_US
dc.description.abstractThe composition of atmospheres and the resulting potential for planetary habitability in the rocky bodies of our Solar System and beyond is strongly controlled by the volatile exchange between their silicate reservoirs and exospheres. The initial budget and speciation of major volatiles, like carbon (C), nitrogen (N) and water (H2O), in the silicate reservoirs and atmospheres was set during the formation stages of rocky bodies. However, the speciation of these major volatiles in reduced silicate melts prevalent during the differentiation stages of rocky bodies and its effect on the partitioning of volatiles between major rocky body reservoirs is poorly known. Here we present SIMS and vibrational spectroscopy (FTIR and Raman) data, determining C solubility, H content, and speciation of mixed C-O-N-H volatiles in graphite saturated silicate glasses from high P (1–7 GPa)-T (1500–2200 °C) experiments reported in Grewal et al., 2019a, Grewal et al., 2019b. The experiments recorded oxygen fugacity (log fO2) between IW–4.3 and IW–0.8. C-O-N-H speciation varied systematically as function of fO2 at any given P-T. We find out that C-N−, , N2, and OH− are the dominant species in the oxidized range (>IW–1.5), along with some contributions from C-H, N-H, and C-O bearing species. Between IW–3.0 and IW–1.5, C is bonded as C-O either in the form of isolated C-O molecules or Fe-carbonyl complexes, or as C-H in hydrocarbons, or as combination of both in esters, while almost all of the H is bonded with the dominant N species, i.e., NH2− or . At the most reduced conditions (<IW–3.0), C is present mostly in the form of C-H bearing species, while anhydrous N3− followed by N-H bearing molecules are the dominant N bearing species. Magma oceans (MOs) in highly reduced bodies like Mercury would contain most of their C as graphite if MO is carbon saturated and the dissolved C and N would be chemically bonded with the silicate network either in the form of anhydrous C4− and N3−, or hydrogenated C-H and N-H bearing species depending on H content of the silicate melts. MOs relevant for Mars, the Moon, Vesta, and angrite parent body would contain C and N mostly in the form of C-O and N-H bearing species, respectively. If the composition of Earth’s accreting material evolved from reduced to oxidized, then initially a significant amount of the C and N budget would be locked in the silicate reservoirs, which would subsequently be released to the proto-atmosphere(s) at later stages. The retention of proto-atmosphere(s) formed by MO degassing on Earth could have provided important precursors for prebiotic chemistry which possibly led to the eventual habitability of our planet. Additionally, based on the dominant speciation of N versus C in silicate melt as a function of fO2, we also predict that is unaffected by fH2 under highly reduced conditions (<IW–3), while is affected. Therefore, caution must be taken during the application of experimentally determined and to nominally anhydrous MOs.en_US
dc.identifier.citationGrewal, Damanveer S., Dasgupta, Rajdeep and Farnell, Alexandra. "The speciation of carbon, nitrogen, and water in magma oceans and its effect on volatile partitioning between major reservoirs of the Solar System rocky bodies." <i>Geochimica et Cosmochimica Acta,</i> 280, (2020) Elsevier: 281-301. https://doi.org/10.1016/j.gca.2020.04.023.en_US
dc.identifier.doihttps://doi.org/10.1016/j.gca.2020.04.023en_US
dc.identifier.urihttps://hdl.handle.net/1911/108766en_US
dc.language.isoengen_US
dc.publisherElsevieren_US
dc.rightsCopyrighted material. All rights reserved.en_US
dc.subject.keywordCarbonen_US
dc.subject.keywordNitrogenen_US
dc.subject.keywordWateren_US
dc.subject.keywordVolatile speciationen_US
dc.subject.keywordSilicate meltsen_US
dc.subject.keywordMagma oceansen_US
dc.subject.keywordEarly atmospheresen_US
dc.subject.keywordPlanetary habitabilityen_US
dc.titleThe speciation of carbon, nitrogen, and water in magma oceans and its effect on volatile partitioning between major reservoirs of the Solar System rocky bodiesen_US
dc.typeJournal articleen_US
dc.type.dcmiTexten_US
dc.type.publicationpublisher versionen_US
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