dc.contributor.author | Rudraswami, N.G. | |
dc.contributor.author | Genge, M.J. | |
dc.contributor.author | Marrocchi, Y. | |
dc.contributor.author | Villeneuve, J. | |
dc.contributor.author | Taylor, S. | |
dc.date.accessioned | 2020-12-31 | |
dc.date.accessioned | 2021-02-09T10:13:13Z | |
dc.date.available | 2020-10-01 | |
dc.date.available | 2021-02-09T10:13:13Z | |
dc.date.issued | 2020 | |
dc.identifier.citation | Journal of Geophysical Research: Planets, vol.125(10); 2020; Article no: e2020JE006414 | |
dc.identifier.issn | 2169-9097 | |
dc.identifier.other | https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020JE006414 | |
dc.identifier.uri | https://doi.org/10.1029/2020je006414 | |
dc.identifier.uri | http://drs.nio.org/drs/handle/2264/8419 | |
dc.description | IF2019 - 3.713 | |
dc.description.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. | |
dc.language | en | |
dc.publisher | American Geophysical Union (AGU) | |
dc.relation.ispartof | J Geophys Res Planets | |
dc.relation.isreferencedby | SCI | |
dc.rights | Only the author version of the copright reserved papers uploaded. Contact drs@nio.org for any complaints regarding copyright violations | |
dc.title | The Oxygen Isotope Compositions of Large Numbers of Small Cosmic Spherules: Implications for Their Sources and the Isotopic Composition of the Upper Atmosphere | |
dc.type | Journal Article | |
dc.affiliation.author | CSIR-National Institute of Oceanography, Dona Paula, Goa, India | |