Presentation #114.05 in the session “Pluto System”.
Photochemical hazes at Pluto were first confirmed by the New Horizons flyby, and model comparisons with the recent measurements suggest aggregated particles grow via coagulation and condensation near 350 km as a result of photochemically derived hydrocarbons. However, the near-surface particle properties are not well constrained, and much remains to be revealed about the Pluto hazes, including but not limited to the monomer size, fractal dimension, and seasonality. This work considers seven haze production rates from KINETICS (the Caltech/JPL 1D photochemical and transport model) to inform the effect of seasonality and solar variability on methane photolysis. We use the microphysical model CARMA, the Community Aerosol Radiation Model for Atmospheres, to investigate haze formation and evolution, and we consider aggregate (fractal dimension of 2.0) and spherical particles. We apply a scattering code on these size distributions in order to derive the extinction, single scattering albedo, and asymmetry parameter as a function of wavelength and altitude. We find that an order of magnitude increase in haze production rate, as would result from the seasonality, results in an order of magnitude change in extinction at each altitude layer, and our results imply that seasonal variations in atmospheric methane abundances should affect the thermal structure of Pluto’s atmosphere. We expect studying the Pluto hazes in different regimes of the world’s seasonality will allow comparisons to be drawn between three worlds: Titan, Triton, and Pluto.