An investigation of Pluto’s troposphere using stellar occultation light curves and an atmospheric radiative–conductive–convective model

We use a radiative–conductive–convective model to assess the height of Pluto’s troposphere, as well as surface pressure and surface radius, from stellar occultation data from the years 1988, 2002, and 2006. The height of the troposphere, if it exists, is less than 1 km for all years analyzed. Pluto has at most a planetary boundary layer and not a troposphere. As in previous analyses of Pluto occultation light curves, we find that the surface pressure is increasing with time, assuming that latitude and longitude variations in Pluto’s atmosphere are negligible. The surface pressure is found to be slightly higher (12.5-2.4+1.9 μbar in 1988, 18.0-1.7+11 μbar in 2002, and 18.5 ± 4.7 μbar in 2006) than in our previous analyses with the troposphere excluded. The surface radius is determined to be 1173-10+20km. Comparison of the minimum reduced chi-squared values between the best-fit radiative–conductive–convective (i.e., troposphere-included) model and best-fit radiative–conductive (i.e., troposphere-excluded) shows that the troposphere-included model is only a slightly better fit to the data for all 3 years. Uncertainties in the small-scale physical processes of Pluto’s lower atmosphere and consequently the functional form of the model troposphere lend more confidence to the troposphere-excluded results.

► The depth of Pluto’s troposphere is unknown.
► We model stellar occultation data using a radiative–conductive–convective model.
► We find Pluto’s troposphere to be less than 1 km in 1988, 2002, and 2006.
► The troposphere-included fits are slightly better than the troposphere-excluded fits.
► We find Pluto’s surface pressure is increasing with time and its radius is 1173 km.