Pluto’s climate modeled with new observational constraints

Pluto has a nitrogen atmosphere in vapor pressure equilibrium with surface ice. N2 is mobile and is transported seasonally even at Pluto’s cold temperatures in the outer Solar System. A thermal model developed by Hansen and Paige in 1996 to model Pluto’s climate has been re-deployed in response to new data and in anticipation of the New Horizons flyby of Pluto in 2015. A number of stellar occultations have been observed in the last 11 years as Pluto has crossed the galactic plane. New Hubble Space Telescope images show a variegated surface. These recent observations allow us to model Pluto’s climate with much tighter constraints. Our findings suggest that Pluto’s atmosphere will not collapse prior to the arrival of New Horizons although pressure will be dropping as N2 condenses on the south polar cap. This finding is in contrast to the Olkin et al. (Olkin et al. [2013]. arXiv1309.0841O) prediction that permanent volatiles in the northern hemisphere maintain Pluto’s atmospheric pressure throughout its orbit. The range of surface pressures predicted for 2015 for nine cases with very good matches to observables is 0.3–3.2 Pa. The best match predicts that New Horizons will detect an atmospheric pressure of 2.4 Pa.