1,- 1Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France (katherine.dale@oca.eu)
- 2Collège de France, CNRS, PSL Univ., Sorbonne Univ., Paris, France
- 3Department of Earth & Environmental Sciences, Michigan State University, East Lansing, USA
- 4Solar System Science & Exploration Division, Southwest Research Institute, Boulder, USA
- 5Bayerisches Geoinstitut, University of Bayreuth, Bayreuth, Germany
Dynamical simulations have long been employed to model terrestrial planet formation. Several frameworks, including the Grand Tack [1], ring model [2], and pebble accretion [3], have successfully reproduced the mass, size, and orbital distribution of the terrestrial planets. Accurately reproducing the chemical composition of these planets must now be paramount in evaluating the success of a model of terrestrial planet formation.
By coupling N-body accretionary scenarios to models of metal-silicate equilibration and impact simulations (using the methods of [4], updated in [5] and [6]), we can assess whether a given scenario can reproduce the composition of the bulk silicate Earth (BSE).
Studies of element partitioning between Earth's mantle and core [7] indicate that, under classical accretion scenarios, Earth initially accreted reduced material before later incorporating oxidised material. Recent work [8] further supports that Earth should have formed from a mixture of oxidised and reduced material to match the composition of the BSE.
Here we focus on the ring model of terrestrial planet formation in which the Earth accretes from a narrow band of material around 1 AU [2], [9], [10], [11]. This implies that all accreting material must originate within the ring, and thus, all oxidation states required to form the Earth were contained within the narrow band.
However, we show that because planetary embryos quickly accrete planetesimals from across the ring's width, they inevitably incorporate both reduced and oxidised material. This leads to early embryos being partially oxidised, which creates a mismatch with the BSE due to the strong dependence of siderophile element partitioning on oxygen fugacity.
We demonstrate that reproducing the BSE requires the initial separation of reduced and oxidised reservoirs until the giant impact stage, where planetary differentiation is controlled by melting from embryo-embryo collisions. The late delivery of oxidised material towards the end of the disc’s lifetime is thus essential for the success of the ring model and likely necessary in all dynamical models of terrestrial planet formation. This demonstrates the importance of considering chemistry when assessing dynamical simulations of planet formation.
References:
[1] Walsh et al., 2011. Nature, vol. 475, Issue 7355.
[2] Hansen et al., 2009. The Astrophysical Journal, vol. 703, Issue 1.
[3] Johansen et al., 2021. Science Advances, vol. 7, Issue 8.
[4] Rubie et al., 2015. Icarus, vol. 248.
[5] Rubie et al., 2025. Earth and Planetary Science Letters, vol. 651.
[6] Dale et al., 2023. Icarus, vol. 406.
[7] Rubie et al., 2011. Earth and Planetary Science Letters, vol. 301.
[8] Dale et al., 2025. Earth and Planetary Science Letters, vol. 658.
[9] Woo et al., 2023. Icarus, vol. 396.
[10] Izidoro et al., 2022. Nature Astronomy, vol. 6.
[11] Nesvorný et al., 2021. The Astronomical Journal, vol. 161, Issue 2.
How to cite: Dale, K., Morbidelli, A., Nathan, G., Woo, J., Nesvorny, D., and Rubie, D.: Oxidation Constraints on Terrestrial Planet Formation in the Ring Model, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–12 Sep 2025, EPSC-DPS2025-737, https://doi.org/10.5194/epsc-dps2025-737, 2025.
