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What materials cover Triton’s surface?

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Clouds in Neptune's atmosphere — Neptune A photograph of clouds in Neptune's atmosphere, taken by Voyager 2 in August 1989. The view is from below the planet's equator, and north is up. The Great Dark Spot (center left) is 13,000 km (8,100 miles)—about the diameter of Earth—in its longer dimension. Accompanying it are bright, wispy clouds thought to comprise methane ice crystals. At higher southern latitudes lies a smaller, eye-shaped dark spot with a light core (bottom left). Just above that spot is a bright cloud dubbed Scooter. Each of these cloud features was seen to travel eastward but at a different rate, the Great Dark Spot moving the slowest.

Triton’s surface is primarily covered by methane and nitrogen ices. Spectroscopic studies have also identified trace amounts of carbon monoxide and carbon dioxide ices.1

While these volatile ices form the visible surface, scientists believe that an underlying layer of water ice exists beneath this thin veneer. This is supported by the presence of large, terraced features that would likely slump without the structural strength provided by water ice at such low temperatures, as well as evidence of past geological activity where subsurface water expanded and fractured the outer crust.1