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Paper: Oxygen Isotopic Heterogeneity in the Solar System: The Molecular Cloud Origin Hypothesis and its Implications for Meteorites and the Planets
Volume: 341, Chondrites and the Protoplanetary Disk
Page: 181
Authors: Kuramoto, K.; Yurimoto, H.
Abstract: The production of 16O-depleted H2O ice in molecular cloud cores has been suggested from observational data and numerical models which reveal selective ultra-violet dissociation of C17,18O isotopomers by the self-shielding effect of C16O, the dominant O-bearing gas species in such star-forming environments. During the evolution of a proto-planetary disk collapsed from such a parent molecular cloud core, the difference in infall velocity between gas and dust grains likely causes the heterogeneous enrichment of H2O-vapor and reduced C-bearing gas species vaporized from ice and organic matter contained in dust grains, respectively. This possibly produces temporal and regional heterogeneity in local mean O-isotopic composition and C/O ratio within the inner disk where the thermo-chemical reprocessing of metallic elements actively occurs prior to accretion to planetesimals. Diversity in O-isotopic composition and redox state observed for meteorites can be interpreted as a consequence of reprocessing in such variable environments within the inner solar nebula. This interpretation predicts that the Sun is 16O-rich, which is consistent with the 16O-rich composition of implanted solar wind extracted from lunar soil. 16O-poor compositions are predicted for the outer planets and their satellites which would provide in future a diagnostic test for models attempting to explain the O-isotopic heterogeneity in the solar system.
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