Pluto’s Color Variations Finally Make Sense: Explained By Methane Ice In The Sun
“The ultraviolet sunlight ionizes methane, setting off a chain of events that creates tholins – red-colored hydrocarbon compounds – that get deposited at various locations. It’s only where fresh, white methane snow covers the tholin-rich regions that a white color reappears. The next time we visit Pluto, this world’s colorscape will appear very different.“
The New Horizons mission surprised everyone last July when it revealed Pluto to be a world that varied significantly in both terrain and color. Instead of a uniform, reddish-hued icy world, it was revealed to have mountains, craters, smooth plains, pitted regions and more, which range in color from white to yellow to deep red. This was initially a mystery, but subsequent analysis has revealed that Pluto’s atmosphere and outer surface consists of a great many volatile molecules, including water, nitrogen and methane. While water ice and nitrogen ice simply sublimate, methane undergoes a complex interaction with ultraviolet light, resulting in the production of tholins, which turn the surface red where they’re deposited. The story is still unfolding, but freshly snow-capped regions and pictures of the entire world support this idea.