A radiogenic heating evolution model for cosmochemically Earth-like exoplanets

Frank, Elizabeth A.; Meyer, B. S.; Mojzsis, Stephen J.

doi:10.1016/j.icarus.2014.08.031

Cited by 70 publications

(67 citation statements)

References 76 publications

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“…We do not include other heat sources such as radiogenic heating, or residual heat from accretion or differentiation. If the abundances of heat-producing elements in the TRAPPIST-1 planets are similar to those in the planets in our solar system, tidal heating will be much larger than radiogenic heating (Frank et al 2014), especially considering the age of the system (∼8 Gyr) (Burgasser & Mamajek 2017). We search for the rock mantle temperature (T eq ) at which the tidal heating rate is equal to the convective heating rate.…”

Section: Methodsmentioning

confidence: 99%

Tidal heating and the habitability of the TRAPPIST-1 exoplanets

Dobos

Barr

Kiss

2019

A&A

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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.

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Section: Methodsmentioning

confidence: 99%

Tidal heating and the habitability of the TRAPPIST-1 exoplanets

Dobos

Barr

Kiss

2019

A&A

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“…For plotting purposes, we saturated the colorscale at high values of dp/dz. since radiogenic heat sources were more abundant (Frank et al 2014).…”

Section: Outgassing Versus Thermal Statementioning

confidence: 99%

Outgassing on stagnant-lid super-Earths

Dorn

Noack

Rozel

2018

A&A

138

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Aims. We explore volcanic outgassing on purely rocky, stagnant-lid exoplanets of different interior structures, compositions and thermal states. We focus on planets in the mass range of 1-8 M C (Earth masses). We derive scaling laws to quantify first-and second-order influences of these parameters on volcanic outgassing after 4.5 Gyrs of evolution. Methods. Given commonly observed astrophysical data of super-Earths, we identify a range of possible interior structures and compositions by employing Bayesian inference modelling. The astrophysical data comprises mass, radius, and bulk compositional constraints, i.e. ratios of refractory element abundances are assumed to be similar to stellar ratios. The identified interiors are subsequently used as input for two-dimensional (2-D) convection models to study partial melting, depletion, and outgassing rates of CO2.Results. In total, we model depletion and outgassing for an extensive set of more than 2300 different super-Earth cases. We find that there is a mass range for which outgassing is most efficient (∼2-3 M C , depending on thermal state) and an upper mass where outgassing becomes very inefficient (∼5-7 M C , depending on thermal state). At small masses (below 2-3 M C ) outgassing positively correlates with planet mass, since it is controlled by mantle volume. At higher masses (above 2-3 M C ), outgassing decreases with planet mass, which is due to the increasing pressure gradient that limits melting to shallower depths. In summary, depletion and outgassing are mainly influenced by planet mass and thermal state. Interior structure and composition only moderately affect outgassing. The majority of outgassing occurs before 4.5 Gyrs, especially for planets below 3 M C . Conclusions. We conclude that for stagnant-lid planets, (1) compositional and structural properties have secondary influence on outgassing compared to planet mass and thermal state, and (2) confirm that there is a mass range for which outgassing is most efficient and an upper mass limit, above which no significant outgassing can occur. Our predicted trend of CO2-atmospheric masses can be observationally tested for exoplanets. These findings and our provided scaling laws are an important step in order to provide interpretative means for upcoming missions such as JWST and E-ELT, that aim at characterizing exoplanet atmospheres.Article number, page 2 of 20

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“…Stars from different galactic pop-N. C. Santos et al: Constraining planet structure and composition from stellar chemistry: trends in different stellar populations ulations may thus present different planet frequencies, and the planets orbiting them may present different composition trends (e.g. Haywood 2008;Adibekyan et al 2012a;Frank et al 2014;Adibekyan et al 2015Adibekyan et al , 2016a.…”

Section: Introductionmentioning

confidence: 99%

Constraining planet structure and composition from stellar chemistry: trends in different stellar populations

Santos

Adibekyan

Dorn

et al. 2017

A&A

102

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Context. The chemical composition of stars that have orbiting planets provides important clues about the frequency, architecture, and composition of exoplanet systems. Aims. We explore the possibility that stars from different galactic populations that have different intrinsic abundance ratios may produce planets with a different overall composition. Methods. We compiled abundances for Fe, O, C, Mg, and Si in a large sample of solar neighbourhood stars that belong to different galactic populations. We then used a simple stoichiometric model to predict the expected iron-to-silicate mass fraction and water mass fraction of the planet building blocks, as well as the summed mass percentage of all heavy elements in the disc. Results. Assuming that overall the chemical composition of the planet building blocks will be reflected in the composition of the formed planets, we show that according to our model, discs around stars from different galactic populations, as well as around stars from different regions in the Galaxy, are expected to form rocky planets with significantly different iron-to-silicate mass fractions. The available water mass fraction also changes significantly from one galactic population to another. Conclusions. The results may be used to set constraints for models of planet formation and chemical composition. Furthermore, the results may have impact on our understanding of the frequency of planets in the Galaxy, as well as on the existence of conditions for habitability.

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A radiogenic heating evolution model for cosmochemically Earth-like exoplanets

Cited by 70 publications

References 76 publications

Tidal heating and the habitability of the TRAPPIST-1 exoplanets

Tidal heating and the habitability of the TRAPPIST-1 exoplanets

Outgassing on stagnant-lid super-Earths

Constraining planet structure and composition from stellar chemistry: trends in different stellar populations

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