What will Pluto’s atmosphere look like ? Predictions from a Global Climate Model including the methane cycle.

Abstract:

On the basis of our experience of modeling the other planetary atmospheres in the solar system, and in particular Mars and Triton, we have developed a Global Climate Model / General Circulation Model (GCM) for Pluto. In addition to a 3D dynamical core which solves the primitive equation of meteorology, the model takes into account the N₂ condensation and sublimation, the vertical turbulent mixing, the radiative transfer through methane and carbon monoxide (using the correlated k method), molecular thermal conduction, and a detailed surface thermal model. The GCM also include a detailed model of the methane cycle, including its sublimation and condensation on the surface and in the atmosphere, mixing by turbulence in the planetary boundary layer, transport by the atmospheric circulation. It consistently predicts the 3D methane abundance in the atmosphere, which is used as an input for the radiative transfer calculations.

This model can be used to make some speculative predictions for the New Horizon flyby in 2015, including the distribution of N₂ and CH₄ ice on the surface and the possible presence of methane ice clouds. Moreover, we evaluate if Titan-like hazes made of organic aerosols could be visible. To address this question, we include a simple parametrization of the formation of organic aerosols resulting from the interaction of methane with the solar UV radiation, and we compute their sedimentation and transport by the general circulation.