Suppression index Ξ as a function of mantle thermal gradient ∆T and bulk modulus K. Regions with Ξ > 1.1 (light-shaded) correspond to > 10% enhancements in escape velocity, indicating strong thermoelastic suppression of atmospheric loss. — astro-ph.EP
The long-term retention of substantial atmospheres in close-in exoplanets presents a major challenge to classical hydrodynamic escape theory, which predicts rapid mass loss under intense stellar irradiation.
In this work, we propose a fully classical, interior-driven suppression mechanism based on thermoelastic contraction of the planetary mantle. By incorporating pressure- and temperature-dependent elastic deformation into the structural evolution of the planet, we demonstrate that radial contraction can lead to measurable increases in surface escape velocity.
We analytically derive a modified escape condition and introduce a dimensionless suppression index Xi that quantifies the extent to which internal mechanical response inhibits atmospheric loss. Numerical simulations across a wide parameter space show that volumetric strain values in the range 0.005 to 0.01 can enhance escape velocities by up to 10 percent, leading to a reduction in energy-limited escape rates by over 50 percent.
When applied to warm mini-Neptunes such as GJ 1214b, K2-18b, and TOI-270c, the model successfully accounts for their persistent atmospheres without invoking exotic stellar conditions or chemical outliers.
Our results indicate that planetary elasticity, often neglected in escape models, plays a first-order role in shaping the atmospheric evolution of close-in worlds. The theory yields specific observational predictions, including suppressed outflow signatures and radius anomalies, which may be testable with JWST, ARIEL, and future spectroscopic missions.
L. Yildiz, D. Kayki, E. Gudekli
Comments: 19 pages, 4 fıgure
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2508.01885 [astro-ph.EP] (or arXiv:2508.01885v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2508.01885
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Submission history
From: Ertan Gudekli
[v1] Sun, 3 Aug 2025 18:37:21 UTC (1,757 KB)
https://arxiv.org/abs/2508.01885
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