Eolianite grain size distributions as a proxy for large changes in planetary atmospheric density

dc.contributor.authorGoosmann, Erik A.
dc.contributor.authorCatling, David C.
dc.contributor.authorSom, Sanjoy M.
dc.contributor.authorAltermann, Wladyslaw
dc.contributor.authorBuick, Roger
dc.date.accessioned2019-06-12T09:21:13Z
dc.date.available2019-06-12T09:21:13Z
dc.date.issued2018-10-08
dc.descriptionA digitized version of the Ahlbrandt (1979) global dune dataset and data for distributions in Figure are available at https://github. com/erikgoosmann/AeolianData.en_ZA
dc.description.abstractAtmospheres are dynamic over geologic timescales, making large changes in planetary air density possible. For the Earth, geological proxies suggest that air density in the Neoarchean was similar to or lower than today. This air density variation possibly affected eolian dune grain sizes by controlling the trajectories of grains though the air. Balancing the fall velocity and threshold friction velocity, a metric separating saltation and suspension transport, suggests that a lower air density could increase the mean grain size of dunes because decreased air drag extends the size range of grains in modified saltation and incipient suspension regimes. Consequently, the dune-forming sand left behind in pure saltation, the dominant dune-forming transport mode, could have coarser grains. We analyzed size distributions of two eolianites from 2.64 and 1.5 Ga (billion years ago) for deviations from modern sand dunes emplaced at sea level, which globally exhibit similar mean grain sizes. Both aeolianites have mean grain sizes within one standard deviation of the modern mean and are not statistically separable at 95% confidence. Overall, this suggests that while air density is important in eolian physics, a factor of 2 to 4 change in density is insufficient to produce an unambiguous grain size signal. This suggests that while eolian dune grain sizes have not significantly changed over the range of Earth’s atmospheric conditions, they could be useful when investigating the order of magnitude changes thought to have occurred on Mars.en_ZA
dc.description.departmentGeologyen_ZA
dc.description.sponsorshipThe Simons Collaboration on the Origin of Life Award 511570 to D. C. C. and by the NASA Astrobiology Institute’s Virtual Planetary Laboratory, grant NNA13AA93A.en_ZA
dc.description.urihttps://agupubs.onlinelibrary.wiley.com/journal/21699100en_ZA
dc.identifier.citationGoosmann, E. A., Catling, D. C., Som, S.M., Altermann, W., & Buick, R. (2018). Eolianite grain size distributions as a proxy for large changes in planetary atmospheric density. Journal of Geophysical Research: Planets, 123, 2506–2526. https://DOI.org/10.1029/2018JE005723.en_ZA
dc.identifier.issn2169-9097 (print)
dc.identifier.issn2169-9100 (online)
dc.identifier.other10.1029/2018JE005723
dc.identifier.urihttp://hdl.handle.net/2263/70154
dc.language.isoenen_ZA
dc.publisherAmerican Geophysical Union (AGU)en_ZA
dc.rights© 2018 American Geophysical Unionen_ZA
dc.subjectEarthen_ZA
dc.subjectMarsen_ZA
dc.subjectNeoarcheanen_ZA
dc.subjectAir densityen_ZA
dc.subjectEolianite grain size distributionen_ZA
dc.subjectPlanetary atmospheric densityen_ZA
dc.titleEolianite grain size distributions as a proxy for large changes in planetary atmospheric densityen_ZA
dc.typeArticleen_ZA

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