Thermal Evolution of Lava Planets Across System Ages: Predictions for Hell of a Survey
Abstract
Ultra-short-period (USP) rocky exoplanets can have dayside temperatures high enough to maintain permanent magma oceans, sitting at the intersection of interior geophysics and atmospheric chemistry. Coupled feedbacks between the molten surface and outgassed atmosphere can sustain or enhance a volatile envelope, while stellar interactions can erode it. Understanding which outcome prevails, and its observable imprint, requires a multi-target approach across planets at different stages of thermal evolution. We present predictions for the five targets of JWST Cycle 4 program 8864: TOI-1807 b, TOI-2260 b, TOI-431 b, TOI-6255 b, and TOI-2431 b. Using the PROTEUS coupled interior-atmosphere framework, we construct a simulation grid and classify outcomes into six categories, defined by the final interior melt state and by whether the planet retains a detectable atmosphere thick enough to redistribute heat to the nightside. For targets retaining a non-negligible volatile envelope, our models predict higher partial pressures for most species when the surface is molten, except for S2, whose enhancement in the solid regime suggests it may serve as a tracer of interior melt state. Despite some targets showing outcomes across multiple scenarios, most tend toward a bare-rock end-member, with global melt fraction ≤ 20\% and atmospheric retention sensitive to escape efficiency. Our analysis reveals a minimum escape efficiency threshold below which volatile envelopes survive under energy-limited escape, constraining the conditions required for atmosphere survival on irradiated rocky planets. These predictions will guide interpretation of MIRI-LRS phase curve observations and identify which targets and features best discriminate between competing geophysical states.
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BibTeX
@misc{sastre2026thermal,
title = {{Thermal Evolution of Lava Planets Across System Ages: Predictions for Hell of a Survey}},
author = {Mariana Sastre and Tim Lichtenberg and Lisa Dang and Anjali Piette and Haiyang S. Wang and Mercedes López-Morales and Thomas Wilson and Charles-Édouard Boukaré and Mahesh Herath and Nicolas Cowan and Md Abdullah Al Zaman and Madyson G. Barber and Casey Brinkman-Traverse and Nicholas Connors and Ian Crossfield and Lina D'Aoust and Oliver Herbort and Leoni Janssen and Mathilde Kervazo and Owen Lammert and Yamila Miguel and Raymond Pierrehumbert and Allona Vazan and Joost P. Wardenier and Sebastian Zieba},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2609.20155},
eprint = {2609.20155},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.20155},
}
RIS
TY - UNPB
TI - Thermal Evolution of Lava Planets Across System Ages: Predictions for Hell of a Survey
AU - Mariana Sastre
AU - Tim Lichtenberg
AU - Lisa Dang
AU - Anjali Piette
AU - Haiyang S. Wang
AU - Mercedes López-Morales
AU - Thomas Wilson
AU - Charles-Édouard Boukaré
AU - Mahesh Herath
AU - Nicolas Cowan
AU - Md Abdullah Al Zaman
AU - Madyson G. Barber
AU - Casey Brinkman-Traverse
AU - Nicholas Connors
AU - Ian Crossfield
AU - Lina D'Aoust
AU - Oliver Herbort
AU - Leoni Janssen
AU - Mathilde Kervazo
AU - Owen Lammert
AU - Yamila Miguel
AU - Raymond Pierrehumbert
AU - Allona Vazan
AU - Joost P. Wardenier
AU - Sebastian Zieba
PY - 2026
DA - 2026/10/20
PB - arXiv
DO - 10.48550/arxiv.2609.20155
UR - https://arxiv.org/abs/2609.20155
AB - Ultra-short-period (USP) rocky exoplanets can have dayside temperatures high enough to maintain permanent magma oceans, sitting at the intersection of interior geophysics and atmospheric chemistry. Coupled feedbacks between the molten surface and outgassed atmosphere can sustain or enhance a volatile envelope, while stellar interactions can erode it. Understanding which outcome prevails, and its observable imprint, requires a multi-target approach across planets at different stages of thermal evolution. We present predictions for the five targets of JWST Cycle 4 program 8864: TOI-1807 b, TOI-2260 b, TOI-431 b, TOI-6255 b, and TOI-2431 b. Using the PROTEUS coupled interior-atmosphere framework, we construct a simulation grid and classify outcomes into six categories, defined by the final interior melt state and by whether the planet retains a detectable atmosphere thick enough to redistribute heat to the nightside. For targets retaining a non-negligible volatile envelope, our models predict higher partial pressures for most species when the surface is molten, except for S_2, whose enhancement in the solid regime suggests it may serve as a tracer of interior melt state. Despite some targets showing outcomes across multiple scenarios, most tend toward a bare-rock end-member, with global melt fraction ≤ 20\% and atmospheric retention sensitive to escape efficiency. Our analysis reveals a minimum escape efficiency threshold below which volatile envelopes survive under energy-limited escape, constraining the conditions required for atmosphere survival on irradiated rocky planets. These predictions will guide interpretation of MIRI-LRS phase curve observations and identify which targets and features best discriminate between competing geophysical states.
ER -