FE-60 IN EUCRITES

Additional evidence for the existence in the early solar system of live Fe-60 has been found in the basaltic achondrite Juvinas. The relative abundance of Fe-60/Fe-56 of approximately 4 x 10(-10) at the time of meteorite solidification is one order of magnitude lower than that previously observed for the eucrite Chervony Kut. This difference corresponds to a approximately 4.7 Ma time interval between closure of the Fe-60-Ni-60 isotopic system in the two meteorites. The factor two higher initial Ni-60/Ni-58 ratio in Juvinas is consistent with this time difference and a common bulk Fe/Ni ratio in the two meteorites. Using the Fe-60-Ni-60 isotope system as a chronometer various models for the evolution of the eucrite parent body of different degrees of complexity are discussed. Regardless of the detailed differences between these models a short time interval of only a few million years between planetary differentiation and basaltic crust formation is indicated.