title: Origin of uranium isotope variations in early solar nebula condensates.
abstract: High-temperature condensates found in meteorites display uranium isotopic variations ((235)U/(238)U), which complicate dating the solar system's formation and whose origin remains mysterious. It is possible that these variations are due to the decay of the short-lived radionuclide (247)Cm (t 1/2 = 15.6 My) into (235)U, but they could also be due to uranium kinetic isotopic fractionation during condensation. We report uranium isotope measurements of meteoritic refractory inclusions that reveal excesses of (235)U reaching ~+6% relative to average solar system composition, which can only be due to the decay of (247)Cm. This allows us to constrain the (247)Cm/(235)U ratio at solar system formation to (1.1 ± 0.3) × 10(-4). This value provides new clues on the universality of the nucleosynthetic r-process of rapid neutron capture.
authors.affiliation: Origins Lab, Department of the Geophysical Sciences, and Enrico Fermi Institute, University of Chicago, Chicago, IL 60637, USA.
authors.forename: François L H
authors.initials: FL
authors.lastname: Tissot
authors.affiliation: Origins Lab, Department of the Geophysical Sciences, and Enrico Fermi Institute, University of Chicago, Chicago, IL 60637, USA.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Dauphas
authors.affiliation: Origins Lab, Department of the Geophysical Sciences, and Enrico Fermi Institute, University of Chicago, Chicago, IL 60637, USA.
authors.forename: Lawrence
authors.initials: L
authors.lastname: Grossman
mesh_terms: D016082:Solar System; D014501:Uranium
chemical_list: D014501:Uranium
keywords: curium-247; fine-grained CAI; group II REE pattern; meteorites; nucleosynthesis; r-process; uranium isotopes