Stratospheric aerosols from CH4 photochemistry on Neptune

The authors have used a combined photochemical-condensation model to study hydrocarbon ices produced from CH4 photolysis in the stratosphere of Neptune. They predict a total stratospheric haze production rate of 4.2 X 10-15 grams cm-2s-1 (75% ethane, 25% acetylene, trace diacetylene). The total production rate is insensitive to within a factor of two to order of magnitude changes in the eddy diffusion coefficient and methane mixing ratio, which is within their estimate of uncertainty for this number. The condensation temperatures are 97K for C4H2, 71 K for C2H2, and 64K for C2H6. Voyager 2 images of Neptune will be able to confirm the presence of stratospheric aerosols and provide constraints on their production rate and location