Datasets of coupled exoplanet interior-atmosphere evolutions for the manuscript "Water oceans on high-density stagnant-lid planets". planet_evolutions directory contains the main data from the study, validations_1Me contains supplementary validation studies evaluating the model sensitivity with respect to changing model parameters. These runs focus on planets with one Earth mass. Each file in the raw_data directoriescontains a full interior and atmosphere evolution of a single planet. The initial parameters are given in the header of each CSV file. The evolution_snapshots.csv files contain snapshots of those planets at random times.
Many super-Earths are on very short orbits around their host star and, therefore, more likely to be tidally locked. Because this locking can lead to a strong contrast between the dayside and nightside surface temperatures, these super-Earths could exhibit mantle convection patterns and tectonics that could differ significantly from those observed in the present-day solar system. The presence of an atmosphere, however, would allow transport of heat from the dayside towards the nightside and thereby reduce the surface temperature contrast between the two hemispheres. On rocky planets, atmospheric and geodynamic regimes are closely linked, which directly connects the question of atmospheric thickness to the potential interior dynamics of the planet. Here, we study the interior dynamics of super-Earth GJ 486b ($R=1.34$ $R_{\oplus}$, $M=3.0$ $M_{\oplus}$, T$_\mathrm{eq}\approx700$ K), which is one of the most suitable M-dwarf super-Earth candidates for retaining an atmosphere produced by degassing from the mantle and magma ocean. We investigate how the geodynamic regime of GJ 486b is influenced by different surface temperature contrasts by varying possible atmospheric circulation regimes. We also investigate how the strength of the lithosphere affects the convection pattern. We find that hemispheric tectonics, the surface expression of degree-1 convection with downwellings forming on one hemisphere and upwelling material rising on the opposite hemisphere, is a consequence of the strong lithosphere rather than surface temperature contrast. Anchored hemispheric tectonics, where downwellings und upwellings have a preferred (day/night) hemisphere, is favoured for strong temperature contrasts between the dayside and nightside and higher surface temperatures.
Redistribution of mass in the Earth due to Pleistocene deglaciation and to present‐day glacial melting induces secular changes in the Earth's gravitational field. The Earth is affected today by the former mechanism because of the viscous memory of the mantle and by the latter because of ongoing surface mass redistribution and related elastic response. A self‐consistent procedure allows us to invert simultaneously for the lower and upper mantle viscosity and for the present‐day mass imbalance in Antarctica and Greenland using the observed time variations of the long‐wavelength gravity field from satellite laser ranging (SLR) analyses. The procedure is based on our normal mode relaxation theory for the forward modeling and a newly developed inversion scheme based on the Levenberg‐Marquardt method. We obtain a large viscosity increase across the 670‐km depth transition zone separating the upper and the lower mantle, with the lower mantle viscosity varying over the range 5 × 10 21 to 10 22 Pa s and the less resolved upper mantle viscosity of the order of 10 20 Pa s. When Antarctica is the only present‐day source, its rate of melting is −240 Gt yr −1 , corresponding to a sea level rise of 0.7 mm yr −1 ; when Greenland is added as a source of ice loss, the rates of melting are −280 Gt yr −1 for Antarctica and −60 Gt yr −1 for Greenland, corresponding to sea level rises of 0.8 and 0.2 mm yr −1 . SLR data indicate that ice melting in the polar regions of the Earth is ongoing.
Energy sources involved in the early stages of planetary formation can cause partial or even complete melting of the mantle of terrestrial bodies leading to the formation of magma oceans. Upon planetary cooling, solidification is expected to take place from the bottom upwards because of the steeper slope of the liquid adiabat with respect to the liquidus (Elkins-Tanton, 2012; Solomatov, 2015). Fractional solidification, in particular, can lead to the formation of a compositional layering that can play a fundamental role for the subsequent long-term dynamics and evolution of the interior (Tosi et al., 2013; Plesa et al., 2014). In order to assess to what extent primordial compositional heterogeneities generated upon magma ocean solidification can be preserved, we investigate the cooling and solidification of a whole-mantle magma ocean along with the conditions that allow solid-state convection to start mixing the mantle before solidification has completed. To this end, we run 2-D numerical simulations in cylindrical geometry using the finite-volume code GAIA (Huttig et al., 2013). We treat the liquid magma ocean in a parametrized fashion while we self-consistently solve the conservation equations of thermochemical convection in the growing solid mantle accounting for pressure-, temperature- and melt-dependent rheology. We consider two end-member cases: fractional crystallization, where melt is instantaneously extracted into the overlying liquid leaving beneath a differentiated mantle, and batch crystallization where melt remains in contact with the silicate matrix throughout solidification causing no differentiation. By testing the effects of different cooling rates and Rayleigh numbers, we show that for a lifetime of the liquid magma ocean between 1 and 10 Myr (Lebrun et al., 2013), the onset of solid state convection prior to complete mantle crystallization is possible and that part or even all of the compositional heterogeneities generated upon fractionation can be erased by efficient mantle stirring (Figure 1). We discuss the consequences of our findings in relation to the early and long-term evolution of compositional heterogeneities generated via fractional crystallization of magma oceans in terrestrial bodies with emphasis on Mars' thermochemical history.
Aims: The long-term carbon cycle for planets with a surface entirely covered by oceans works differently from that of the present-day Earth because inefficient erosion leads to a strong dependence of the weathering rate on the rate of volcanism. In this paper, we investigate the long-term carbon cycle for these planets throughout their evolution. Methods: We built box models of the long-term carbon cycle based on CO$_2$ degassing, seafloor-weathering, metamorphic decarbonation, and ingassing and coupled them with thermal evolution models of stagnant lid and plate tectonics planets. Results: The assumed relationship between the seafloor-weathering rate and the atmospheric CO$_2$ or the surface temperature strongly influences the climate evolution for both tectonic regimes. For a plate tectonics planet, the atmospheric CO$_2$ partial pressure is characterised by an equilibrium between ingassing and degassing and depends on the temperature gradient in subduction zones affecting the stability of carbonates. For a stagnant lid planet, partial melting and degassing are always accompanied by decarbonation, such that the combined carbon content of the crust and atmosphere increases with time. Whereas the initial mantle temperature for plate tectonics planets only affects the early evolution, it influences the evolution of the surface temperature of stagnant lid planets for much longer. Conclusions: For both tectonic regimes, mantle cooling results in a decreasing atmospheric CO$_2$ partial pressure. For a plate tectonics planet this is caused by an increasing fraction of subduction zones that avoid crustal decarbonation, and for stagnant lid planets this is caused by an increasing decarbonation depth. This mechanism may partly compensate for the increase of the surface temperature due to increasing solar luminosity with time and hereby contribute to keep planets habitable in the long-term.
