Estimation of the tidal heating in the TRAPPIST-1 planets. Influence of the internal structure

Abstract

With the arrival of JWST observations of the TRAPPIST-1 planets, it is timely to reassess the contribution of tidal heating to their heat budget. JWST thermal phase curves could reveal endogenic heating through an anomalously high nightside temperature, providing an opportunity to estimate tidal heating. In this study, we revisit the tidal heating of these planets and propose a simple method to compute the tidal heating profile across a broad range of parameters. Our approach leverages a known formulation for synchronously rotating planets on low-eccentricity orbits and the fact that the profile shape depends solely on internal structure. We calculate the tidal heating contributions for all T-1 planets, with a particular focus on the impact of internal structure and eccentricity uncertainties on their total heat budget. Although the masses and radii of these planets are well constrained, degeneracies remain in their internal structure and composition. For volatile-poor planets of silicate-rock compositions, we investigate the role of core iron content by exploring a range of core sizes. For each structure, we compute the degree-two gravitational Love number, $k_2$, and the corresponding tidal heating profiles. We assume sub-solidus temperatures profiles that are decoupled from interior heat production, which means our estimates are conservative and likely represent minimum values. We find that the tidal heat flux for T-1b and c can exceed Io's heat flux, with uncertainties primarily driven by eccentricity. These high fluxes may be detectable with JWST. For T-1f to g, the tidal flux remains below Earth's geothermal flux, suggesting that tidal heating is unlikely to be the dominant energy source. For planets d and e, however, tidal heating likely dominates their heat budget, potentially driving intense volcanic and tectonic activity, which could enhance their habitability prospects.

14 pages, 6 figures. Accepted in A&A

References in corpus (14)

• Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1
• Mass-Radius Relationships for Solid Exoplanets
• Detailed Models of super-Earths: How well can we infer bulk properties?
• Thermal emission from the Earth-sized exoplanet TRAPPIST-1 b using JWST
• Coreless Terrestrial Exoplanets
• Early 2017 observations of TRAPPIST-1 with $\text{Spitzer}$
• A review of possible planetary atmospheres in the TRAPPIST-1 system
• Magma oceans and enhanced volcanism on TRAPPIST-1 planets due to induction heating
• TRAPPIST-1: Global Results of the Spitzer Exploration Science Program {\it Red Worlds}
• Tidal Heating and the Habitability of the TRAPPIST-1 Exoplanets
• Water Condensation Zones around Main Sequence Stars
• The habitability of stagnant-lid Earths around dwarf stars
• Tides between the TRAPPIST-1 planets
• Sporadic Spin-Orbit Variations in Compact Multi-planet Systems and their Influence on Exoplanet Climate