Kavli Affiliate: Paul D. Asimow
| First 5 Authors: Damanveer S. Grewal, Nicole X. Nie, Bidong Zhang, Andre Izidoro, Paul D. Asimow
| Summary:
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.
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