We can often use our knowledge of planet Earth to explain things we see on other worlds, although we may have to modify physics to account for a different temperature or a dim atmosphere. But planetary scientists cannot always assume that a familiar landscape feature has formed in a familiar way.
When the New Horizons spacecraft gave us our first close look at Pluto, there were alien wonders in abundance. But there were also the mountain tops dusted with something bright, very similar to the snow-capped peaks of the Earth. On Earth, these snow caps are produced by increased precipitation as the air rises over the mountains and cools, combined with colder temperatures at higher elevations.
On Pluto, that explanation cannot work, for several reasons. First, the temperatures in general to increase as it rises a few kilometers from the surface of Pluto due to the gases that absorb solar energy. Winds also tend to blow downslope as the colder surface cools the air near it, making it denser. So what forms the bright dusting and how does it get there?
West of Pluto̵
To understand why methane ice would form there, the researchers turned to a climate model of the dwarf planet. The model allowed methane and nitrogen to form ice (or vanish into gas), and the researchers targeted conditions at the time of the New Horizons visit. By simply entering physics and topography, the model successfully produces methane ice on Cthulhu’s mountains and craters. Many places can see the formation of methane frost at night but disappear during the day. But a higher concentration of methane gas at higher altitudes leads to a net accumulation on mountain tops during that daily cycle.