Oxidation state and volatile element evolution during equilibrium planetary accretion: The case study for mars and vesta
Abstract
The Mercury-Venus-Earth-Mars-Vesta planetary suite exhibits large variations in oxidation state as defined by the Fe to FeO ratio (i.e. core to silicate ratio), with increasingly oxygen-depleted bodies toward the centre of the solar system. As undifferentiated materials (i.e., chondrites) likely display a similar heliocentric FeO-gradient, planetary and chondritic oxidation states should be related in this respect. We develop an approach wherein, the equilibrium oxygen redistribution during gas - silicate melt - molten metal alloy during differentiation is resolved for bodies of various compositions and sizes. As a case study, three chondritic end-members were considered: enstatite, ordinary, and carbonaceous. A broad range of planetary oxidation states are obtained that encompass the above-mentioned planetary suite. The oxidation state during the growth of small bodies (<2000 km in radius) of constant bulk composition is affected by metal-vapour carbon redistribution, whereas on larger bodies, the incorporation of hydrogen, oxygen and silicon in the core prevails, causing the convergence toward a putative universal magma ocean FeO content. A dual regime is observed for the water content in the silicate magma ocean, which increases up to a planetary radius of ∼3000 km, whereas in larger bodies, hydrogen incorporation into the core brings about dehydration of the complementary silicate mantles. The accretion of ordinary chondrites perfectly matches the oxidation state of Mars and produces a core with C-H-S-N contents matching the Martian core density as suggested by the Insight missions. Finally, Vesta's oxidation state seemingly requires an H₂O-rich oxidizing component during the formation of planetesimals.
Related
- Metal-Silicate Segregation During Planetary Accretion: Limited Iron Emulsification through intermediate Impacts
- Volatile depletion in rocky planets as a chemical fingerprint of hybrid accretion
- Planetary Accretion Is Less Frequent in Wide Binaries: Evidence from Metal-Enriched White Dwarfs in DESI DR1
- Planetary Accretion Is Less Frequent in Wide Binaries: Evidence from Metal-enriched White Dwarfs in DESI DR1
- Volatile-element depletion in rocky planets as a purity spectrum of a single information field: An information-dynamics reinterpretation of hybrid accretion
BibTeX
@article{gaillard2026oxidation,
title = {{Oxidation state and volatile element evolution during equilibrium planetary accretion: The case study for mars and vesta}},
author = {Fabrice Gaillard and Yves Marrocchi and Grégory Rogerie and Mohamed A. Bouhifd and Camille Bernard and Mathieu Roskosz},
journal = {Earth and Planetary Science Letters},
year = {2026},
month = sep,
doi = {10.1016/j.epsl.2026.120245},
url = {https://insu.hal.science/insu-05721688v2},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Oxidation state and volatile element evolution during equilibrium planetary accretion: The case study for mars and vesta
AU - Fabrice Gaillard
AU - Yves Marrocchi
AU - Grégory Rogerie
AU - Mohamed A. Bouhifd
AU - Camille Bernard
AU - Mathieu Roskosz
PY - 2026
DA - 2026/09/14
JO - Earth and Planetary Science Letters
DO - 10.1016/j.epsl.2026.120245
UR - https://insu.hal.science/insu-05721688v2
AB - The Mercury-Venus-Earth-Mars-Vesta planetary suite exhibits large variations in oxidation state as defined by the Fe to FeO ratio (i.e. core to silicate ratio), with increasingly oxygen-depleted bodies toward the centre of the solar system. As undifferentiated materials (i.e., chondrites) likely display a similar heliocentric FeO-gradient, planetary and chondritic oxidation states should be related in this respect. We develop an approach wherein, the equilibrium oxygen redistribution during gas - silicate melt - molten metal alloy during differentiation is resolved for bodies of various compositions and sizes. As a case study, three chondritic end-members were considered: enstatite, ordinary, and carbonaceous. A broad range of planetary oxidation states are obtained that encompass the above-mentioned planetary suite. The oxidation state during the growth of small bodies (<2000 km in radius) of constant bulk composition is affected by metal-vapour carbon redistribution, whereas on larger bodies, the incorporation of hydrogen, oxygen and silicon in the core prevails, causing the convergence toward a putative universal magma ocean FeO content. A dual regime is observed for the water content in the silicate magma ocean, which increases up to a planetary radius of ∼3000 km, whereas in larger bodies, hydrogen incorporation into the core brings about dehydration of the complementary silicate mantles. The accretion of ordinary chondrites perfectly matches the oxidation state of Mars and produces a core with C-H-S-N contents matching the Martian core density as suggested by the Insight missions. Finally, Vesta's oxidation state seemingly requires an H₂O-rich oxidizing component during the formation of planetesimals.
SN - 0012-821X
ER -