The uranium isotopic composition of the Earth and the Solar System

The average 238U/235U of the investigated meteorite groups (including data compiled from the literature) and terrestrial basalts is 137.794 ± 0.027 (at a 95% student's t confidence level, including all propagated uncertainties) and represents the best estimate for the U isotope composition of the Earth and the Solar System. This value may be used for U-Pb and Pb-Pb dating of Solar System materials, provided the precise U isotope composition of the sample is unknown. Compared to Pb-Pb ages that were determined with the previously assumed value for 238U/235U (137.88), this new value results in an age adjustment of −0.9 Ma.