Accretion of the earliest inner solar system planetesimals beyond the water-snowline
arXiv:2408.17032 · doi:10.1038/s41550-023-02172-w
Abstract
How and where the first generation of inner solar system planetesimals formed remains poorly understood. Potential formation regions are the silicate condensation line and water-snowline of the solar protoplanetary disk. Whether the chemical compositions of these planetesimals align with accretion at the silicate condensation line (water-free and reduced) or water-snowline (water-bearing and oxidized) is, however, unknown. Here we use Fe/Ni and Fe/Co ratios of magmatic iron meteorites to quantify the oxidation states of the earliest planetesimals associated with non-carbonaceous (NC) and carbonaceous (CC) reservoirs, representing the inner and outer solar system, respectively. Our results show that the earliest NC planetesimals contained substantial amounts of oxidized Fe in their mantles (3-19 wt% FeO). In turn, we argue that this required the accretion of water-bearing materials into these NC planetesimals. The presence of substantial quantities of moderately and highly volatile elements in their parent cores is also inconsistent with their accretion at the silicate condensation line and favors instead their formation at or beyond the water-snowline. Similar oxidation states in the early-formed parent bodies of NC iron meteorites and those of NC achondrites and chondrites with diverse accretion ages suggests that the formation of oxidized planetesimals from water-bearing materials was widespread in the early history of the inner solar system.
28 pages, 3 main figures, 6 Extended data figures, 4 Extended data tables
References in corpus (10)
- Towards planetesimals: dense chondrule clumps in the protoplanetary nebula
- A water budget dichotomy of rocky protoplanets from Al-heating
- Contemporary formation of early solar system planetesimals at two distinct radial locations
- Terrestrial planet formation from lost inner solar system material
- Planetesimal rings as the cause of the Solar System's planetary architecture
- Early evolution of the solar accretion disk inferred from Cr-Ti-O isotopes in individual chondrules
- Molecule sublimation as a tracer of protostellar accretion: Evidence for accretion bursts from high angular resolution C18O images
- Early volatile depletion on planetesimals inferred from C-S systematics of iron meteorite parent bodies
- Isotopic evolution of the inner Solar System inferred from molybdenum isotopes in meteorites
- Internal or external magma oceans in the earliest protoplanets -- perspectives from nitrogen and carbon fractionation