In Pluto, remember, it’s snowing methane. It has an atmosphere about 150 kilometers high and it’s so cold that the atmosphere is frozen, so that all the methane day flashes.
Pluto’s atmosphere is separated into two layers can be seen in the picture (taken by New Horizons). One of about 90 km and a 60 km high.
By all appearances, hydrocarbons (mainly methane) that are suspended in the upper layers, and precipitate fall in the lower as snow. Falling and rushing, and they condense heavy hydrocarbons, which is what “snow”.
These heavy hydrocarbons, ultraviolet (remember that the atmosphere does not stop them) are converted into Tholins are no more molecules with much nitrogen, falling on the surface (they dark) give the color to Pluto has appeared in the images.
What a beautiful thing is the universe, although many do not mind shit.