We report new Zr isotope evidence for live 92Nb (mean life: τ̄92Nb = 52 Myr) within the early solar system resulting in (92Nb/93Nb)initial ≈ 10-3. The meteoritic minerals rutile and zircon have, respectively, very high and very low Nb/Zr ratios and are ideal for exploring the 92Nb-92Zr chronometer. Rutiles exhibit high positive ∈ 92Zr (∼ 14-36) while a zircon has a negative ∈92Zr (∼-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 ∼80-220 Myr subsequent to the origin of the solar system. The initial 92Nb/92Mo for the solar system is broadly compatible with a model of uniform production if the 92Nb/92Mo production ratio for Type II supernova (SNII) sources with neutrino-driven winds is used. Data for all the now extinct p-process nuclides (92Nb, 97Tc, and 146Sm) are consistent with these isotopes being derived by uniform production from SNII sources and a free decay interval of ∼ 10 Myr. Consideration of a range of models indicates that the average p-process production ratio of 92Nb/92Mo needs to be at least in the range of 0.06-0.25.
- ISM: abundances
- Nuclear reactions, nucleosynthesis, abundances
- Solar system: formation
- Supernovae: general