Cooling of an early Earth magma ocean in interaction with the atmosphere

It is likely that a magma ocean has formed early in the Earth history and in particular just after the big impact that is thought to have formed the Moon 4.48 Ga ago (Halliday, 2008). This ocean interacts with the atmosphere through degassing upon crystallization. Hence a strong coupling should exist between the two envelopes (atmosphere and cooling magma ocean). We developed a 1D convective model of a cooling magma ocean that we coupled with a 1D radiative- convective model of a primitive atmosphere (Marcq et al., EPSC 2011). Our main objective is to build a coupled model of a cooling magma ocean interacting with a primitive atmosphere, in turn, allowing for an estimation of the cooling time of the magma ocean. We present here some preliminary results of this coupled magma ocean / atmospheric model. We show that cooling time depends on the amount of volatiles released from the interior and is of order of 1 to 2 million years. The model will be coupled in the near future with an impact and hydrodynamic escape model. Subsequently, this will enable us to determine the time required for the primitive atmosphere to condense its water vapor thus determining the period during which the water oceans may have formed.