Volatile depletion in rocky planets as a chemical fingerprint of hybrid accretion
Abstract
Volatile depletion in rocky planets relative to their host stars is commonplace in both the Solar System and exoplanetary systems, yet the connections between planet formation and composition remain elusive. Here we model devolatilization during pebble accretion in combination with collisional growth from volatile-depleted planetesimals to explore the formation pathways of Earth and Mars. Using Bayesian inference, we find that bulk silicate Earth is best reproduced by ≳75% contribution from two protoplanets formed via pebble accretion, supplemented by up to ∼25% material from planetesimals that are compositionally akin to the asteroid Vesta. Using instead a planetesimal volatile-depletion curve that is not observed among known meteorite parent bodies would allow the planetesimal contribution to reach 40+15−14%. In comparison, bulk silicate Mars reflects 27±5% pebble-accreted material and 73±5% Vesta-like planetesimals. We identify volatile depletion as a chemical fingerprint of hybrid accretion, in which both pebble accretion and collisional assembly contribute to terrestrial planet growth. By quantitatively linking formation pathways to volatile budgets, our findings demonstrate how planetary accretion histories can be inferred from elemental signatures, with broad implications for interpreting the chemical diversity of rocky exoplanets.
Versions
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BibTeX
@misc{wang2026volatile,
title = {{Volatile depletion in rocky planets as a chemical fingerprint of hybrid accretion}},
author = {Haiyang S. Wang and Anders Johansen and Ziyan Xu and Marie-Luise Steinmeyer and Michiel Lambrechts and Elishevah van Kooten and Chao-Chin Yang and Zhaohuan Zhu and Dante S. Lauretta and Martin Bizzarro},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2608.24407},
eprint = {2608.24407},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.24407},
}
RIS
TY - UNPB
TI - Volatile depletion in rocky planets as a chemical fingerprint of hybrid accretion
AU - Haiyang S. Wang
AU - Anders Johansen
AU - Ziyan Xu
AU - Marie-Luise Steinmeyer
AU - Michiel Lambrechts
AU - Elishevah van Kooten
AU - Chao-Chin Yang
AU - Zhaohuan Zhu
AU - Dante S. Lauretta
AU - Martin Bizzarro
PY - 2026
DA - 2026/09/25
PB - arXiv
DO - 10.48550/arxiv.2608.24407
UR - https://arxiv.org/abs/2608.24407
AB - Volatile depletion in rocky planets relative to their host stars is commonplace in both the Solar System and exoplanetary systems, yet the connections between planet formation and composition remain elusive. Here we model devolatilization during pebble accretion in combination with collisional growth from volatile-depleted planetesimals to explore the formation pathways of Earth and Mars. Using Bayesian inference, we find that bulk silicate Earth is best reproduced by ≳75% contribution from two protoplanets formed via pebble accretion, supplemented by up to ∼25% material from planetesimals that are compositionally akin to the asteroid Vesta. Using instead a planetesimal volatile-depletion curve that is not observed among known meteorite parent bodies would allow the planetesimal contribution to reach 40^+15_−14%. In comparison, bulk silicate Mars reflects 27±5% pebble-accreted material and 73±5% Vesta-like planetesimals. We identify volatile depletion as a chemical fingerprint of hybrid accretion, in which both pebble accretion and collisional assembly contribute to terrestrial planet growth. By quantitatively linking formation pathways to volatile budgets, our findings demonstrate how planetary accretion histories can be inferred from elemental signatures, with broad implications for interpreting the chemical diversity of rocky exoplanets.
ER -