Cosmogenic nuclides in the Kosice meteorite: Experimental investigations and Monte Carlo simulations

Results of nondestructive gamma-ray analyses of cosmogenic radionuclides (Be-7, Na-22, Al-26, Sc-46, V-48, Mn-54, Co-56, Co-57, Co-58, and Co-60) in 19 fragments of the Kosice meteorite are presented and discussed. The activities varied mainly with position of fragments in the meteoroid body, and with fluxes of cosmic-ray particles in the space affecting radionuclides with different half-lives. Monte Carlo simulations of the production rates of Co-60 and Al-26 compared with experimental data indicate that the pre-atmospheric radius of the meteoroid was 50 +/- 5 cm. In two Kosice fragments, He, Ne, and Ar concentrations and isotopic compositions were also analyzed. The noble-gas cosmic-ray exposure age of the Kosice meteorite is 5-7 Myr, consistent with the conspicuous peak (or doublet peak) in the exposure age histogram of H chondrites. One sample likely contains traces of implanted solar wind Ne, suggesting that Kosice is a regolith breccia. The agreement between the simulated and observed Al-26 activities indicate that the meteoroid was mostly irradiated by a long-term average flux of galactic cosmic rays of 4.8 particles cm(-2) s(-1), whereas the short-lived radionuclide activities are more consistent with a flux of 7.0 protons cm(-2) s(-1) as a result of the low solar modulation of the galactic cosmic rays during the last few years before the meteorite fall.