Giant Impacts Preferentially Remove Low-mass Atmospheres: A Generalised Scaling Law for Impact-driven Atmospheric Loss
- 1University of Bristol
Abstract
Impact-driven atmospheric loss plays a key role in shaping the diversity of planetary atmospheres. However, existing prescriptions for calculating loss from a given impact neglect the critical role of atmospheric mass on loss, and thus often severely miscalculate the extent of loss. Using 3D smoothed particle hydrodynamics simulations, we quantify atmospheric loss during giant impacts onto planets with 1%–20% mass fraction atmospheres and show that less massive (lower-pressure) atmospheres are significantly easier to remove. We derive a new scaling law for atmospheric loss that includes the effects of atmospheric mass and is applicable to collisions between volatile-poor planetary embryos through to super-Earths and sub-Neptunes. Applying our scaling law to N -body simulations of solar system formation, we show that including the coupling between atmospheric mass and loss efficiency results in significantly more atmosphere removal. Substantial atmospheric loss events are common for smaller planets (≲0.6 M ⊕ ), while even roughly Earth-mass bodies lose 30%–100% of their atmospheres through multiple impacts. We also show that atmospheric loss during the Moon-forming impact strongly depends on both the pre-impact atmospheric mass and impact style. For a representative ∼100 bar pre-impact atmosphere, Earth could have lost between 20%–80% of its atmosphere. In any system that undergoes a phase of giant impacts, the atmospheres of its host planets will be unavoidably shaped by the stochasticity of impacts. Our new scaling law can be readily incorporated into models of planet formation and system-wide evolution, offering new insights into the origins of planetary diversity.
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BibTeX
@article{roche2026giant,
title = {{Giant Impacts Preferentially Remove Low-mass Atmospheres: A Generalised Scaling Law for Impact-driven Atmospheric Loss}},
author = {Matthew J. Roche and Simon J. Lock and Philip J. Carter and Zoë M. Leinhardt},
journal = {The Astrophysical Journal Letters},
year = {2026},
month = nov,
doi = {10.3847/2041-8213/aeb26a},
url = {https://iopscience.iop.org/article/10.3847/2041-8213/aeb26a},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Giant Impacts Preferentially Remove Low-mass Atmospheres: A Generalised Scaling Law for Impact-driven Atmospheric Loss
AU - Matthew J. Roche
AU - Simon J. Lock
AU - Philip J. Carter
AU - Zoë M. Leinhardt
PY - 2026
DA - 2026/11/05
JO - The Astrophysical Journal Letters
DO - 10.3847/2041-8213/aeb26a
UR - https://iopscience.iop.org/article/10.3847/2041-8213/aeb26a
AB - Impact-driven atmospheric loss plays a key role in shaping the diversity of planetary atmospheres. However, existing prescriptions for calculating loss from a given impact neglect the critical role of atmospheric mass on loss, and thus often severely miscalculate the extent of loss. Using 3D smoothed particle hydrodynamics simulations, we quantify atmospheric loss during giant impacts onto planets with 1%–20% mass fraction atmospheres and show that less massive (lower-pressure) atmospheres are significantly easier to remove. We derive a new scaling law for atmospheric loss that includes the effects of atmospheric mass and is applicable to collisions between volatile-poor planetary embryos through to super-Earths and sub-Neptunes. Applying our scaling law to N -body simulations of solar system formation, we show that including the coupling between atmospheric mass and loss efficiency results in significantly more atmosphere removal. Substantial atmospheric loss events are common for smaller planets (≲0.6 M ⊕ ), while even roughly Earth-mass bodies lose 30%–100% of their atmospheres through multiple impacts. We also show that atmospheric loss during the Moon-forming impact strongly depends on both the pre-impact atmospheric mass and impact style. For a representative ∼100 bar pre-impact atmosphere, Earth could have lost between 20%–80% of its atmosphere. In any system that undergoes a phase of giant impacts, the atmospheres of its host planets will be unavoidably shaped by the stochasticity of impacts. Our new scaling law can be readily incorporated into models of planet formation and system-wide evolution, offering new insights into the origins of planetary diversity.
SN - 2041-8213
SN - 2041-8205
ER -