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

2015; Wiley; Volume: 50; Issue: 5 Linguagem: Inglês

10.1111/maps.12380

1945-5100

Pavel P. Povinec, J. Masarik, I. Sýkora, A. Kováčik, Juraj Beňo, M. M. M. Meier, R. Wieler, M. Laubenstein, V. Porubčan,

Nuclear Physics and Applications

Abstract Results of nondestructive gamma‐ray analyses of cosmogenic radionuclides ( 7 Be, 22 Na, 26 Al, 46 Sc, 48 V, 54 Mn, 56 Co, 57 Co, 58 Co, and 60 Co) in 19 fragments of the Košice 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 60 Co and 26 Al compared with experimental data indicate that the pre‐atmospheric radius of the meteoroid was 50 ± 5 cm. In two Košice fragments, He, Ne, and Ar concentrations and isotopic compositions were also analyzed. The noble‐gas cosmic‐ray exposure age of the Košice 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 Košice is a regolith breccia. The agreement between the simulated and observed 26 Al 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.