3d Modeling of Pluto's Atmosphere

An Atmospheric General Circulation Model for Pluto with Predictions for New Horizons

Author:

Zalucha

Abstract:

Results are presented from a 3-D Pluto general circulation model (PGCM) that includes a subsurface model and volatile cycle. Conductive heating and cooling are present, as is non-local thermodynamic equilibrium (non-LTE) heating by methane at 2.3 and 3.3 microns, non-LTE cooling by heating by methane at 7.6 microns, and LTE CO rotational line cooling. This model is novel in that it has both detailed subsurface and atmospheric model components. Yet, there is little dependence of the model results on surface albedo, emissivity, or conductivity. Predictions are also provided for the Alice and REX instruments on New Horizons and for ground-based stellar occultations. Due to the weak temperature gradients, Alice (both solar and background star consultations) and REX are predicted to observe nearly the same temperature profiles on immersion and emersion. In the stratosphere, differences of up to 20 K are possible, while at higher altitudes (100-350 km), the differences are as large as 10 K. For both methane concentration and initial surface pressure, it should be possible to distinguish between the 0.2 and 1.0 methane concentrations and 8 and 24 microbar initial surface concentrations used here. For the ground-based stellar occultation, there is a detectable difference between light curves with the different methane concentrations used here, but not for the initial surface pressures.