Simulating Pluto’s atmosphere with hybrid fluid/kinetic models Justin Erwin Recent and expected spacecraft exploration of the planets and moons of our solar system have greatly increased interest in atmospheric escape. My motivation has been to produce an accurate model of Pluto’s atmosphere, which includes atmospheric loss by escape. The results will be both predictive for and tested against data obtained during the New Horizon encounter, which will occur in late 2015. To accurately capture the nature of the escape and structure of Pluto’s thermosphere and exosphere, I have developed a model of Pluto’s upper atmosphere by connecting a fluid model to a molecular kinetic model. Using this hybrid model I have shown that the atmosphere is much more extended than previously predicted and the escape is not supersonic, as in comet or stellar atmospheres. Rather, it is closer to the evaporative Jeans model of escape. Furthermore, I have developed a self-consistent model of Pluto’s full atmosphere, including both the stratospheric radiative heating and cooling that prevail in the lower atmosphere, as well as the UV heating and the cooling by atmospheric escape.