Volatile degassing and chemical speciation of the C-O-H system in the Earth Magma Ocean scenario

Abstract

During the early phase of its evolution the Earth was likely characterized by the presence of a magma ocean or several large magma ponds. In this period there was a strong interaction between the interior differentiation process, the silicate melt phase and the atmosphere. The aim of this research is to investigate the degassing of volatiles in the C-O-H system in the presence of a magma ocean and the subsequent development of the early Earth's atmosphere. The volatile outgassing and the chemical speciation were investigated throughout numerical model simulations. Specifically, we analyze the volatile transition from the mantle to the atmosphere by using the equilibrium and mass balance method. The most representative reactions for the outgassing process are simulated at pressures, temperatures and redox states which are characteristic for the magma ocean scenario. The gas chemical speciation is deeply influenced by both the thermodynamic properties and the redox state. In a reduced ambient and for low temperatures the main gas species are: CO, CH4 and H2. On the other hand in oxidizing condition the principal gas species are H2O and CO2. In addition, the pressure played a central role during the evolution of the magma ocean and the crust formation. The pressure has a strong effect on the solubility of the gas phases within the silicate melt and the related availability of outgassed volatile species. Lastly, considering an extension of the present scope, this analytical technique has the potential also to characterize the volatile behavior of planetary bodies subject to high internal pressures such as massive solid exoplanets.