2025ApJ...994..262Y

The survival of volatile-rich atmospheres on close-in exoplanets challenges classical escape models. We identify a fully classical, interior-driven correction: thermoelastic contraction of the planetary mantle slightly increases the gravitational binding energy and the effective escape threshold. Incorporating pressure and temperature-dependent elastic deformation, we define a dimensionless suppression index ${\rm{\Xi }}\equiv {(1-{\epsilon }_{{\rm{V}}}/3)}^{-1/2}$ that links interior strain to escape dynamics. Across super-Earth and sub-Neptune regimes, realistic volumetric strains (ϵ_V ∼ 10^–3-10^–2) enhance the escape velocity by 0.02%-0.17%, yielding ≲1% reductions in energy-limited mass-loss rates. Critically, the Jeans regime amplifies this effect through its exponential sensitivity to v_esc: for representative super-Earth parameters, thermoelastic contraction alone suppresses the Jeans escape rate by up to ∼18%. This establishes mantle elasticity as a small but physically robust correction to escape theory and a novel interior-atmosphere coupling channel. For instance, in the case of K2-18b, the predicted contraction-induced signal corresponds to ∼30 ppm at 1.4 μm, within the reach of JWST/NIRSpec in ∼5 transits. We outline observational tests-particularly with JWST and ARIEL-where high signal-to-noise transmission spectroscopy could, in favorable cases, probe these suppression signatures and place constraints on deep planetary structure.