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dc.contributor.authorItcovitz, Jonathan
dc.contributor.authorRae, ASP
dc.contributor.authorCitron, RI
dc.contributor.authorStewart, ST
dc.contributor.authorSinclair, CA
dc.contributor.authorRimmer, Paul
dc.contributor.authorShorttle, Oliver
dc.date.accessioned2022-05-20T15:04:57Z
dc.date.available2022-05-20T15:04:57Z
dc.date.issued2022-05-01
dc.date.submitted2021-11-01
dc.identifier.issn2632-3338
dc.identifier.otherpsjac67a9
dc.identifier.otherac67a9
dc.identifier.otheraas35792
dc.identifier.urihttps://www.repository.cam.ac.uk/handle/1810/337348
dc.description.abstractImpacts may have had a significant effect on the atmospheric chemistry of the early Earth. Reduced phases in the impactor (e.g., metallic iron) can reduce the planet's H$_2$O inventory to produce massive atmospheres rich in H$_2$. Whilst previous studies have focused on the interactions between the impactor and atmosphere in such scenarios, we investigate two further effects, 1) the distribution of the impactor's iron inventory during impact between the target interior, target atmosphere, and escaping the target, and 2) interactions between the post-impact atmosphere and the impact-generated melt phase. We find that these two effects can potentially counterbalance each other, with the melt-atmosphere interactions acting to restore reducing power to the atmosphere that was initially accreted by the melt phase. For a $\sim10^{22}\,\mathrm{kg}$ impactor, when the iron accreted by the melt phase is fully available to reduce this melt, we find an equilibrium atmosphere with H$_2$ column density $\sim10^4\,\mathrm{moles\,cm^{-2}}$ ($p\mathrm{H2}\sim120\,\mathrm{bars}\mathrm{,}~X_\mathrm{H2}\sim0.77$), consistent with previous estimates. However, when the iron is not available to reduce the melt (e.g., sinking out in large diameter blobs), we find significantly less H$_2$ ($7\times10^2-5\times10^3\,\mathrm{moles\,cm^{-2}}$, $p\mathrm{H2}\lesssim60\,\mathrm{bars}\mathrm{,}~X_\mathrm{H2}\lesssim0.41$). These lower H$_2$ abundances are sufficiently high that species important to prebiotic chemistry can form (e.g., NH3, HCN), but sufficiently low that the greenhouse heating effects associated with highly reducing atmospheres, which are problematic to such chemistry, are suppressed. The manner in which iron is accreted by the impact-generated melt phase is critical in determining the reducing power of the atmosphere and re-solidified melt pool in the aftermath of impact.
dc.languageen
dc.publisherAmerican Astronomical Society
dc.subject500
dc.subjectPlanetary Science
dc.titleReduced atmospheres of post-impact worlds: The early Earth
dc.typeArticle
dc.date.updated2022-05-20T15:04:57Z
prism.issueIdentifier5
prism.publicationNameThe Planetary Science Journal
prism.volume3
dc.identifier.doi10.17863/CAM.84762
dcterms.dateAccepted2022-04-15
rioxxterms.versionofrecord10.3847/PSJ/ac67a9
rioxxterms.versionVoR
rioxxterms.licenseref.urihttp://creativecommons.org/licenses/by/4.0/
dc.contributor.orcidItcovitz, Jonathan [0000-0003-2079-8171]
dc.contributor.orcidRimmer, Paul [0000-0002-7180-081X]
dc.contributor.orcidShorttle, Oliver [0000-0002-8713-1446]
dc.identifier.eissn2632-3338
dc.publisher.urlhttp://dx.doi.org/10.3847/PSJ/ac67a9
pubs.funder-project-idSTFC (ST/T505985/1)
pubs.funder-project-idScience and Technology Facilities Council (2277520)
cam.issuedOnline2022-05-20


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