• Login
    View Item 
    •   DSpace Home
    • Institute's contributions
    • Scholarly literature
    • View Item
    •   DSpace Home
    • Institute's contributions
    • Scholarly literature
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    The Oxygen Isotope Compositions of Large Numbers of Small Cosmic Spherules: Implications for Their Sources and the Isotopic Composition of the Upper Atmosphere

    Thumbnail
    View/Open
    J_Geophy_Res_Plane_125_e2020JE006414.pdf.pdf (1.896Mb)
    J_Geophy_Res_Plane_125_e2020JE006414_Appe.pdf.PDF (511.8Kb)
    Date
    2020
    Author
    Rudraswami, N.G.
    Genge, M.J.
    Marrocchi, Y.
    Villeneuve, J.
    Taylor, S.
    Metadata
    Show full item record
    Abstract
    Cosmic spherules are micrometeorites that melt at high altitude as they enter Earth’s atmosphere and their oxygen isotope compositions are partially or completely inherited from the upper atmosphere, depending on the amount of heating experienced and the nature of their precursor materials. In this study, the three oxygen isotope compositions of 137 cosmic spherules are determined using 277 insitu analyses by ion probe. Our results indicate a possible correlation between an increasing average δ 18O compositions of silicate dominated (S-type) spherules along the series scoriaceous<porphyritic<barred<cryptocrystalline<glass<CAT spherules (~12, 20, 22, 25, 26 and 50‰). This is consistent with the evolution of oxygen isotopes by mass fractionation owing to increased average entry heating thus suggests mass fractionation dominates changes in isotopic composition, with atmospheric exchange being less significant. The  17O values of spherules, therefore, are mostly preserved and suggest that ~80% of particles are samples of C-type asteroids. The genetic relationships between different S-types can also be determined with scoriaceous, barred and cryptocrystalline-spherules mostly having low  17O values (≤0‰) mainly derived from CC-like sources, whilst porphyritic spherules mostly have positive  17O (>0‰) are largely derived from ordinary chondrite (OC)-like sources related to S(IV)-type asteroids. Glass and CAT-spherules have variable  17O values indicating they formed by intense entry heating of both CC and OC-like materials. I-type cosmic spherules have a narrow range of δ17O (~20–25‰) and δ18O (~38–48‰) values, with  17O (~0‰) suggesting their oxygen is obtained entirely from the Earth’s atmosphere, albeit with significant mass fractionation owing to evaporative heating. Finally, G-type cosmic spherules have unexpected isotopic compositions demostrate little mass-fractionation from a CC-like source. The results of this study provide a vital assessment of the wider population of extraterrestrial dust arriving at the Earth.
    URI
    https://doi.org/10.1029/2020je006414
    http://drs.nio.org/drs/handle/2264/8419
    Collections
    • Scholarly literature [9074]

    DSpace software copyright © 2002-2016  DuraSpace
    Contact Us | Send Feedback
    Theme by 
    Atmire NV
     

     

    Browse

    All of DSpaceCommunities & CollectionsBy Issue DateAuthorsTitlesSubjectsThis CollectionBy Issue DateAuthorsTitlesSubjects

    My Account

    LoginRegister

    DSpace software copyright © 2002-2016  DuraSpace
    Contact Us | Send Feedback
    Theme by 
    Atmire NV