Abundance , distribution , and origin of 60 Fe in the solar protoplanetary disk

Meteorites contain relict decay products of short-lived radionuclides that were present in the protoplanetary disk when asteroids and planets formed. Several studies reported a high abundance of Fe (t1/21⁄42.6270.04 Myr) in chondrites (Fe/Fe 6 10 ), suggesting that planetary materials incorporated fresh products of stellar nucleosynthesis ejected by one or several massive stars that whole rocks and constituents of differentiated achondrites (ureilites, aubrites, HEDs, and angrites), unequilibrated ordinary chondrites Semarkona (LL3.0) and NWA 5717 (ungrouped petrologic type 3.05), metal-rich carbonaceous chondrite Gujba (CBa), and several other meteorites (CV, EL H, LL chondrites; IIIAB, IVA, IVB iron meteorites). We derive from these measurements a much lower initial Fe/Fe ratio of (11.572.6) 10 9 and conclude that Fe was homogeneously distributed among planetary bodies. This low ratio is consistent with derivation of Fe from galactic background (Fe/FeE2.8 10 7 in the interstellar medium from g-ray observations) and can be reconciled with high Al/Al 5 10 5 in chondrites if solar material was contaminated through winds by outer layers of one or several massive stars (e.g., a Wolf–Rayet star) rich in Al and poor in Fe. We present the first chronological application of the Fe–Ni decay system to establish the time of core formation on Vesta at 3:7þ2:5 1:7 Myr after condensation of calcium–aluminum-rich inclusions (CAIs). Published by Elsevier B.V.