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 about 4 x 10 exp -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 an about 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.