Characterization of Early Magma Oceans Degassing Efficiencies
Abstract
Due to their blanketing effect, planetary atmospheres strongly influence the thermal history of rocky planets and play a crucial role in determining their surface conditions and their potential habitability.
Planetary atmospheres are commonly thought to result from a rapid outgassing, during the cooling and the solidification of an early magma ocean stage. The vigorous convection is believed to effectively stir the magma ocean, so that the volatiles initially dissolved in the melt are assumed to reach the surface fast enough for degassing to be efficient. Thus, the exsolved volatiles are usually considered to be in equilibrium with the atmospheric pressures. However, such a common assumption has not been tested on the basis of fluid dynamics considerations. Indeed, the dynamics of the magma ocean controls the distribution of volatiles in the molten mantle and thus, the amount of volatiles reaching the surface and outgassed. Therefore, we tested the hypothesis of an efficient early degassing on terrestrial planets. To this end, we conducted a series of numerical experiments in 2D Cartesian domains, where we modeled the dynamics of convecting magma oceans using a finite- volume approach. We systematically varied the Rayleigh and the Prandtl numbers to identify how the convection regimes and their associated patterns influence the amount of magma reaching the degassing depth. For each experiment considered we characterized the degassing of the convective magma ocean. Finally, we propose simple scalings to explain our model results.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMMR51D0071S
- Keywords:
-
- 1030 Geochemical cycles;
- GEOCHEMISTRY;
- 1060 Planetary geochemistry;
- GEOCHEMISTRY;
- 3630 Experimental mineralogy and petrology;
- MINERALOGY AND PETROLOGY;
- 8409 Atmospheric effects;
- VOLCANOLOGY