Cm/U, Th/U, and ^(235)U/^(238)U in Meteorites

The relative abundances of the actinides, ^(247)Cm, ^(244)Pu, ^(235)U, ^(238)U, and ^(232)Th are important for the estimation of the duration of galactic nucleosynthesis and the time interval between the termination of the last contributing "r" process nucleosynthetic event and formation of the solar system. ^(247)Cm is particularly important because of its half life (1.56 x 10^7y). As ^(247)Cm is an extinct nuclide, the basic evidence for its presence must come from observed shifts in the ^(235)U/^(238)U ratio and anomalies in ^(207)Pb/^(206)Pb and U-Pb ages in early solar system samples.