Thermal Models of Inhomogeneously Accreted Meteorite Parent Bodies

Abstract

THERMAL calculations on planetary models, together with cooling rate data from studies of Ni diffusion gradients in iron meteorites, have been used to establish constraints on the possible dimensions of meteorite parent bodies1–3. Previously these models assumed spherical chondritic bodies with uniform distribution of radioactive heat sources, although redistribution of heat sources upon melting has been considered. Core formation has usually been regarded as a subsequent metamorphic event. But recent studies suggest that iron was fractionated early in the planetary formation process and that the terrestrial planets were inhomogeneously accreted4. Therefore, considering the differences in thermal properties and distribution of radioactive heat sources that result from initial core formation followed by silicate accretion, we present here thermal calculations on a set of models of meteorite parent bodies in which initial formation of a Ni-Fe core is assumed.