Description
During the early stages of the evolution of rocky planets, heat due to accretion, core formation, and radioactive decay has likely melted their silicate mantles, creating global magma oceans. As the magma ocean cools down and solidifies, dissolved volatiles are progressively outgassed, forming a secondary atmosphere. Greenhouse gases in this atmosphere form an insulating blanket that controls much of the evolution of the magma ocean, making interior-atmosphere coupled evolutionary models crucial for understanding this interplay.
Due to vigorous convection of the magma, these models typically assume efficient outgassing of the magma ocean, in chemical equilibrium with the atmosphere. However, the outgassing efficiency can be limited by the fact that fluid parcels containing dissolved volatiles must reach small pressures in order for bubbles to be formed and volatiles outgassed.
We apply this out-of-equilibrium (i.e., non-instantaneous) outgassing scheme to a 1D parametrized model coupled with a radiative-convective atmosphere. This model was calibrated using joint laboratory experiments and Finite-Volume numerical modeling at finite Prandtl number, allowing us to derive scalings for convective cooling and outgassing efficiency.
We systematically vary initial concentrations in CO2 and H2O and planetary sizes over broad ranges, assuming limited solid-melt segregation in the partially molten viscous mush.
With this coupled model, we then investigate the influence of out-of-equilibrium outgassing on the cooling time of the solidifying magma ocean, along with their consequences on planetary atmospheres and surfaces, and habitability. Key findings include the formation of a water ocean on early Earth less than 10 000 years after the beginning of the magma ocean phase, the possible existence of large volatile reservoirs in the mantle, and new constraints on exoplanet compositions that allow for habitability.
| Speaker information | PhD 2nd year |
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