Geophysical Evolution of Exoplanetst

The magma ocean phase describes the early stage of rocky planets, during which the entire planet is molten due to heat generated by accretion processes. In the case of short-period exoplanets inside the runaway greenhouse limit, this phase may last Gyrs, until the inventory of major primordial volatiles, such as H2O, CO2, and H2, is exhausted. The internal evolution of these planets is influenced by various factors, including the exchange of volatiles between the molten planetary interior and the atmosphere. This exchange significantly impacts planetary climate, exoplanet bulk densities, surface conditions, and long-term geodynamic activity by controlling greenhouse effects, surface water stability, and atmospheric composition.

Impact of varying redox states on crystallization and atmospheric composition of rocky exoplanets. (in prep.)

The evolution of the magma ocean phase and the interaction between interior and atmosphere has focused dominantly on Earth-like (oxidized) conditions, or alternatively on strongly hydrogen-rich (sub-Neptune) environments, neglecting that vast parameter space likely covered in the transition compositional regime. The work I will present here, focuses on modeling the evolving interaction of atmospheres and interiors under different redox (composition) conditions. Using a coupled computational framework of the planetary interior and atmosphere, I studied the detailed evolution of the magma ocean phase, aiming to understand the crystallization sequence and the atmospheric composition in equilibrium with long-lived magma oceans.

Geodynamical Regimes in Earth-like Exoplanets (Master thesis)

Solid-state convection of rocky planetary mantles is essential to a planet's habitability over geological timescales. The starting point of main events, such as plate tectonics, is mainly controlled by this heat transfer efficiency. To understand better how this particular tectonic regime came about in Earth's evolution, and how this can be extrapolated to our understanding of the dynamical regime of Earth-like exoplanets and especially their outgassing, it is necessary to investigate under which conditions Earth-sized planetary mantles can produce enough melt that might deliver volatiles to the surface. In this study, I model the internal structure of Earth-sized exoplanets that serve as a basis for 2D heat transfer numerical simulations to explore the parameter space of different silicate mantle sizes and dynamical regimes. In this way, I investigated the optimal candidates for internal structure configurations and compositions, to break the primitive basaltic crust considering different heat sources. I applied my model to the particular case of the TRAPPIST-1 planets to constrain tidal dissipation that can be produced within their mantle according to different core sizes. I showed that Earth-like exoplanets with big cores are the best candidates to produce melt efficiently and consequently deliver more water content to the atmosphere.

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Drifts of the substellar points of the TRAPPIST-1 planets. Revol A, et al. (2024)

Accurate modeling of tidal interactions is crucial for interpreting recent JWST observations of the thermal emissions of TRAPPIST- 1 b and c and for characterizing the surface conditions and potential habitability of the other planets in the system. Indeed, the rotation state of the planets, driven by tidal forces, significantly influences the heat redistribution regime. Due to their proximity to their host star and the estimated age of the system, the TRAPPIST-1 planets are commonly assumed to be in a synchronization state. In this work, we present the recent implementation of the co-planar tidal torque and forces equations within the formalism of Kaula in the N-body code Posidonius. This enables us to explore the hypothesis of synchronization using a tidal model well suited to rocky planets. We studied the rotational state of each planet by taking into account their multi-layer internal structure computed with the code Burnman. Our simulations show that the TRAPPIST-1 planets are not perfectly synchronized but oscillate around the synchronization state. Planet-planet interactions lead to strong variations on the mean motion and tides fail to keep the spin synchronized with respect to the mean motion. As a result, the substellar point of each planet experiences short oscillations and long-timescale drifts that lead the planets to achieve a synodic day with periods varying from 55 years to 290 years depending on the planet..

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