The initial solar system abundance of Fe and early core formation of the first asteroids.

High-precision Ni isotope analyses of the differentiated andesitic meteorite Erg Chech 002 (EC 002), the oldest known crustal fragment of a planetesimal, show that short-lived Fe was present in the early solar system with an initial Fe/Fe ratio of (7.71 ± 0.47) × 10, which is five times more precise than previous estimates and is proposed to be the reference value for further studies. Using this ratio, the Ni isotopic composition of EC 002 implies that metal segregation in the source of the EC 002 parental melts took place [Formula: see text] million years (Myr) after solar system formation, and similar very early metal-silicate differentiation ages are obtained for 4-Vesta ([Formula: see text] Myr) and the angrite parent body ([Formula: see text] Myr). Such an early age dictates a specific accretion and differentiation history for the EC 002 parent body, with metal segregation occurring at relatively low temperatures (1000° to 1200°C), followed by a high-temperature silicate melting event.