Cosmic radiation ages and space erosion. 2. The iron meteorites

Previously measured 36Ar/36Cl, 38Ar/39Ar, and 41K/40K cosmic radiation ages of eight iron meteorites are compared. In all cases the potassium age is higher, and in four cases the discordancy is beyond the experimental error limits. The discordancy cannot be removed by considerations of argon-diffusion loss, and considerations based solely on a long-term variation of the cosmic-ray intensity are not satisfactory. A time-independent space erosion effect of 2 x 10-8 cm/yr can resolve the discrepancy and bring all the radiation ages into agreement within a conservative error limit of ± 10%. (author)