Interior-surface-atmosphere interactions in the Earth's Magma Ocean stage

Abstract

During the early phase of its evolution, the Earth was likely characterized by a magma ocean stage. The main aim of this research is to improve the present knowledge about the interior-surface-atmosphere interactions during the early Earth history. We analyse the interaction between magma ocean degassing and crystallization and the consequent development of the Earth's early atmosphere by combining several modeling approaches. Specifically, the late stages of the magma ocean and the volatile solubility are modeled using petrological software tools to investigate the chemical evolution of the melt during the fractional crystallization and the volatile content. Moreover, the equilibrium constants and mass balance method was employed to calculate the outgassed volatile composition of the C-O-H system, considering the oxygen fugacity of the melt as one of the main factors that affects the gases chemical speciation. This method shows an interesting aspect of the interaction between the solid/melt phase and the gas phase since the volatile final composition is directly related to the melt oxygen fugacity. We observe that under reduced conditions the volatile composition is dominated by H2 and CO. On the other hand, in an oxidized ambient the main species are H2O and CO2. Furthermore, since the thermal and chemical evolution of the magma ocean is tied to the planetary cooling rate we developed a coupling sequence of 1D models that enable the calculation of a (steam) atmosphere structure over a temperature range that corresponds to a molten silicate surface. Simulating the atmospheric structure, we calculate the outgoing long-wavelength radiation, and hence the planetary cooling rate at the topmost atmosphere is determined. Lastly, from our preliminary results it can be claimed that a multidisciplinary approach helps to shed light on magma ocean degassing/crystallization, on subsequent development of the atmosphere, and on the early Earth's evolution.