Origin of uranium isotope variations in early solar nebula condensates

By François L. H. Tissot, Nicolas Dauphas, Lawrence Grossman

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

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Supplementary Materials (PDF)

“High-temperature condensates found in meteorites display uranium isotopic variations (235U/238U), which complicate dating the solar system’s formation, the origin of which 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 (1.1 ± 0.3) × 10−4. This value provides new clues on the universality of the rapid neutron capture r-process of nucleosynthesis.”