Volcanic outgassing and early atmosphere build-up

Kurzfassung

The early phase of the Earth´s evolution was characterized by the presence of a magma ocean or several magma ponds. The heat generated during the late accretion of the Earth and soon after the Moon forming impact was likely high enough to produce the thermodynamics conditions for a total or partially molten mantle. The focus of the present research is to analyse the magma ocean volcanic outgassing in the C-O-H system and the related development of the Earth´s atmosphere. The gas chemical speciation and the atmosphere evolution are investigated through numerical model simulations. By using the “Equilibrium and mass balance method”, the volatile chemical outgassing is analysed for a range of pressures, temperatures, and oxidation states which are representative for the magma ocean scenario. The results collected through this method show the variation in the volatile composition due to the redox conditions of the melt during the outgassing process. For reduced states (QIF and IW buffers) the dominant outgassed phases are CO and H2. On the other hand, in oxidizing states (NiNiO and QFM buffers) the principal volatile species are H2O and CO2. The results show the strong connection between the interior of the planet and the development of the early atmosphere. The gas speciation model is coupled with a 2D mantle convection model, with which we will investigate the volatile pathways from the mantle to the atmosphere. Our coupled interior-speciation model will analyse the build-up of early Earth's atmosphere for different redox evolution scenarios starting after the magma ocean solidification phase until the end of the late Archaean.