The changing mantle FeO and SiO2 of 8 Earth analogues as they grow through the simulation.
Here we show that, if the terrestrial planets formed from a narrow ring of planetesimals, this condition is not fulfilled, whatever heliocentric gradient of oxidation is assumed in the ring.
The reason is that planetary embryos quickly accrete planetesimals from the whole width of the ring, incorporating both reduced and oxidised material.
We demonstrate that reproducing the BSE composition requires reduced and oxidised reservoirs to remain segregated until embryo formation is almost complete.
The delivery of oxidised material to the terrestrial planet-forming ring towards the end of the disc’s lifetime is therefore a key requirement of any successful dynamical model of terrestrial planet formation.
The changing mantle FeO and SiO2 of 8 Earth analogues as they grow through the simulation. The black dashed line and the grey band show the BSE concentrations of FeO and SiO2 (Palme and O’Neill, 2003) and the uncertainties on these values. The left-hand figure contains an insert that allows for a clearer view of the point at which the embryo masses reach 1 Earth Mass. — astro-ph.EP
The present-day solar system comprises meteorites with varying oxidation levels, derived from different parent bodies.
Previous studies (e.g. Rubie et al., 2011) of the partitioning of siderophile elements between mantle and core during planetary growth and differentiation showed that Earth must accrete reduced bodies first and oxidised bodies later. Here we show that, if the terrestrial planets formed from a narrow ring of planetesimals, this condition is not fulfilled, whatever heliocentric gradient of oxidation is assumed in the ring.
The reason is that planetary embryos quickly accrete planetesimals from the whole width of the ring, incorporating both reduced and oxidised material. The partially oxidised state of all planetary embryos leads to mismatches with the composition of the bulk silicate Earth (BSE) because oxygen fugacity strongly affects the partitioning of siderophile elements.
We demonstrate that reproducing the BSE composition requires reduced and oxidised reservoirs to remain segregated until embryo formation is almost complete. The delivery of oxidised material to the terrestrial planet-forming ring towards the end of the disc’s lifetime is therefore a key requirement of any successful dynamical model of terrestrial planet formation.
Katherine I. Dale, Alessandro Morbidelli, Gabriel Nathan, Jason Woo, David Nesvorný, David C. Rubie
Comments: Accepted in Icarus, 20 pages (including appendix), 11 figures (including appendix) and two tables (appendix)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2605.31081 [astro-ph.EP] (or arXiv:2605.31081v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2605.31081
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Submission history
From: Katherine Dale
[v1] Fri, 29 May 2026 09:48:38 UTC (2,354 KB)
https://arxiv.org/abs/2605.31081
Astrobiology, Exoplanet,
