Production Rates for Noble-Gas Isotopes in Eucrites

To get cosmic-ray exposure ages of meteorites from measured concentrations of cosmic-ray-produced ("cosmogenic") noble-gas isotopes, production rates for those isotopes are needed. The best production rates take into consideration the composition of the meteorite and the "shielding" of the sample (the pre-atmospheric size and shape of the meteoroid and the sample s location in the meteoroid). For ordinary chondrites, there have been many sets of measurements to establish production systematics. The Ne-22/Ne-21 is often used to help to get shielding-dependent production rates. We report here numerical simulations for the production of isotopes of the light noble gases He, Ne, and Ar in both basaltic and cumulate eucrites for several sizes.