Supernova sources and the Nb-92-Zr-92 p-process chronometer

We report new Zr isotope evidence for live Nb-92 (mean life: <(tau)over bar >(92Nb) = 52 Myr) within the early solar system resulting in (Nb-92/Nb-93)( initial) approximate to 10(-3). The meteoritic minerals rutile and zircon h ave, respectively, very high and very low Nb/Zr ratios and are ideal for ex ploring the Nb-92-Zr-92 chronometer. Rutiles exhibit high positive epsilon( 92Zr) (similar to 14-36) while a zircon has a negative epsilon(92Zr) (simil ar to-4), as would be expected if 92Nb was live in the early solar system. The meteoritic rutiles appear to be young, with apparent times of formation of similar to 80-220 Myr subsequent to the origin of the solar system. The initial Nb-92/Mo-92 for the solar system is broadly compatible with a mode l of uniform production if the 92Nb/92Mo production ratio for Type II super nova (SNII) sources with neutrino-driven winds is used. Data for all the no w extinct p-process nuclides (Nb-92, Tc-97 and Sm-146) are consistent with these isotopes being derived by uniform production from SNII sources and a free decay interval of similar to 10 Myr. Consideration of a range of model s indicates that the average p-process production ratio of 92Nb/92Mo needs to be at least in the range of 0.06-0.25.