From the interior to the atmosphere: volatile chemical speciation and Earth magma ocean evolution.

The early history of the Earth was characterized by a magma ocean stage. The principal aimof this research is a better investigation of the magma ocean interior-surface-atmosphereinteractions by combining several modelling approaches. We analyse the degassing rateduring the early phase of the magma ocean and the related chemical speciation of theoutgassed volatile phases. Moreover, by simulating the structure of the atmosphere wecalculate the cooling rate at its top, and therefore of the whole planet. The degassing rate is provided by a 1D interior-atmosphere coupled model that resolvesthe magma ocean solidification and its thermal evolution. The two volatile species H2O andCO2 included are dissolved in the melt and they are degassed when their solubility in themelt is exceeded. Progressive solidification of the mantle ensures an increase in thecumulative atmospheric mass. Moreover, the volatile chemical speciation of the C-O-Hsystem is analysed with the equilibrium and mass balance method. Since the gaschemical composition is affected by the volatile availability of the magma oceanand by the melt oxygen fugacity, this method shows the direct link between theinterior and the development of the atmosphere. We observed that under reducedcondition (QIF and IW mineral buffers) the dominant outgassed gas phases are H2and CO. On the other hand, with an oxidizing ambient (NiNiO and QIF mineralbuffers) the principal gas phases are H2O and CO2. Furthermore, the structure and theevolution of the atmosphere are investigated. We calculate the outgoing longwaveradiation at the top of the atmosphere using the line-by-line radiative transfer codeGARLIC. The results of the present research show that an interdisciplinary approach is a key pointto shed light on the interior-surface-atmosphere interactions and on the early Earth evolution.The transition of the volatiles from the interior to the surface was affected both by the thermaland redox evolution of the mantle. These interactions influenced the composition of theearly atmosphere and the related cooling rate of the planet. Lastly, considering anextension of the present scope, this analytical technique has the potential also tocharacterise the volatile behaviour and the thermal evolution of solid exoplanets. [ABSTRACT FROM AUTHOR]