We describe here a model of formation of the core and the early history of
Earth based on recent experimental mineralogical data. In a nebular setting
, where differentiated planetesimals with their iron cores were plentiful,
hot condensing solids mixed with the planetesimal irons and formed the soli
d proto-core (Fe-Ni-S-C). FeO from unmixing in magnesiowustite and from a d
issociation of perovskite in the newly accreted mantle concentrated at the
core-mantle interface and reacted with the nascent core. The interface grew
to form the liquid core (Fe-Ni-O-S-C) at the expense of the solid proto-co
re and the formation of much of the outer core was complete within the firs
t 500 million years. The model is consistent with geochemical data and has
important implications for the dynamics of the inner core.