A short timescale for terrestrial planet formation from Hf-W chronometry of meteorites

Determining the chronology for the assembly of planetary bodies in the early Solar System is essential for a complete understanding of star- and planet-formation processes. Various radionuclide chronometers (applied to meteorites) have been used to determine that basaltic lava flows on the surface of the asteroid Vesta formed within 3 million years (3 Myr) of the origin of the Solar System(1-3). Such rapid formation is broadly consistent with astronomical observations of young stellar objects, which suggest that formation of planetary systems occurs within a few million years after star formation(4,5). Some hafnium-tungsten isotope data, however, require that Vesta formed later 6 (similar to16 Myr after the formation of the Solar System) and that the formation of the terrestrial planets took a much longer time(7-10) (62(-14)(+4504) Myr). Here we report measurements of tungsten isotope compositions and hafnium-tungsten ratios of several meteorites. Our measurements indicate that, contrary to previous results(7-10), the bulk of metal-silicate separation in the Solar System was completed within <30 Myr. These results are completely consistent with other evidence for rapid planetary formation(1-5), and are also in agreement with dynamic accretion models(11-13) that predict a relatively short time (∼10 Myr) for the main growth stage of terrestrial planet formation.