Research ArticleSPACE SCIENCES

Origin of uranium isotope variations in early solar nebula condensates

Science Advances  04 Mar 2016:
Vol. 2, no. 3, e1501400
DOI: 10.1126/sciadv.1501400

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Abstract

High-temperature condensates found in meteorites display uranium isotopic variations (235U/238U), 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 247Cm (t1/2 = 15.6 My) into 235U, 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 235U reaching ~+6% relative to average solar system composition, which can only be due to the decay of 247Cm. This allows us to constrain the 247Cm/235U ratio at solar system formation to (7.0 ± 1.6) × 10−5. This value provides new clues on the universality of the nucleosynthetic r-process of rapid neutron capture.

Keywords
  • nucleosynthesis
  • meteorites
  • uranium isotopes
  • curium-247
  • r-process
  • fine-grained CAI
  • group II REE pattern

This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial license, which permits use, distribution, and reproduction in any medium, so long as the resultant use is not for commercial advantage and provided the original work is properly cited.

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