Tidal Heating and the Habitability of the TRAPPIST-1 Exoplanets

Context. New estimates of the masses and radii of the seven planets orbiting the ultracool M-dwarf TRAPPIST-1 star permit improved modelling of their compositions, heating by tidal dissipation, and removal of tidal heat by solid-state convection.

Aims. Here, we compute the heat flux due to insolation and tidal heating for the inner four planets. Methods. We apply a Maxwell viscoelastic rheology to compute the tidal response of the planets using the volume-weighted average of the viscosities and rigidities of the metal, rock, high-pressure ice and liquid water/ice I layers.

Results. We show that TRAPPIST-1d and e can avoid entering a runaway greenhouse state. Planet e is the most likely to support a habitable environment, with Earth-like surface temperatures and possibly liquid water oceans. Planet d also avoids a runaway greenhouse, if its surface reflectance is at least as high as that of the Earth. Planets b and c, closer to the star, have heat fluxes high enough to trigger a runaway greenhouse and support volcanism on the surfaces of their rock layers, rendering them too warm for life. Planets f, g, and h are too far from the star to experience significant tidal heating, and likely have solid ice surfaces with possible subsurface liquid water oceans.

Vera Dobos, Amy C. Barr, László L. Kiss
(Submitted on 11 Feb 2019)

Comments: accepted for publication in A&A, 5 pages, 3 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1902.03867 [astro-ph.EP] (or arXiv:1902.03867v1 [astro-ph.EP] for this version)
Submission history
From: Vera Dobos
[v1] Mon, 11 Feb 2019 13:34:28 UTC (1,037 KB)
https://arxiv.org/abs/1902.03867
Astrobiology