• DOI:10.1051/0004-6361/201731992
• Corpus ID: 119516532

Interior Structures and Tidal Heating in the TRAPPIST-1 Planets

@article{Barr2018InteriorSA,
  title={Interior Structures and Tidal Heating in the TRAPPIST-1 Planets},
  author={Amy C. Barr and Vera Dobos and L{\'a}szl{\'o} L. Kiss},
  journal={Astronomy and Astrophysics},
  year={2018},
  volume={613}
}

• A. Barr, V. Dobos, L. Kiss
• Published 15 December 2017
• Geology, Physics
• Astronomy and Astrophysics

With seven planets, the TRAPPIST-1 system has the largest number of exoplanets discovered in a single system so far. The system is of astrobiological interest, because three of its planets orbit in the habitable zone of the ultracool M dwarf. Assuming the planets are composed of non-compressible iron, rock, and H$_2$O, we determine possible interior structures for each planet. To determine how much tidal heat may be dissipated within each planet, we construct a tidal heat generation model using a single uniform viscosity and rigidity for each planet based on the planet's composition. With the exception of TRAPPIST-1c, all seven of the planets have densities low enough to indicate the presence of significant H$_2$O in some form. Planets b and c experience enough heating from planetary tides to maintain magma oceans in their rock mantles; planet c may have eruptions of silicate magma on its surface, which may be detectable with next-generation instrumentation. Tidal heat fluxes on planets d, e, and f are lower, but are still twenty times higher than Earth's mean heat flow. Planets d and e are the most likely to be habitable. Planet d avoids the runaway greenhouse state if its albedo is $\gtrsim$ 0.3. Determining the planet's masses within $\sim0.1$ to 0.5 Earth masses would confirm or rule out the presence of H$_2$O and/or iron in each planet, and permit detailed models of heat production and transport in each planet. Understanding the geodynamics of ice-rich planets f, g, and h requires more sophisticated modeling that can self-consistently balance heat production and transport in both rock and ice layers.