Origin of uranium isotope variations in early solar nebula condensates

TL;DR

This study investigates uranium isotope variations in meteorite condensates, attributing them to decay of 247Cm, which constrains early Solar System nucleosynthesis and impacts dating methods.

Contribution

It provides the first direct measurement linking uranium isotope anomalies to 247Cm decay, offering new constraints on Solar System formation and nucleosynthetic processes.

Findings

Uranium isotope excesses of ~+6% detected in meteorites

Constrained 247Cm/235U ratio at Solar System formation to (7.0 +- 1.6) x 10^-5

Results suggest universality of r-process nucleosynthesis

Abstract

High temperature condensates found in meteorites display uranium isotopic variations (235U/238U) that complicate dating of the formation of the Solar System and whose origin remains mysterious. It is possible that these variations are due to decay of the short-lived radionuclide 247Cm (t1/2=15.6 Myr) 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 decay of 247Cm. This allows us to constrain the 247Cm/235U ratio at Solar System formation to (7.0 +- 1.6) x 10-5. This value provides new clues on the universality of nucleosynthetic r-process of rapid neutron capture.