Triton’s surface, according to a new crater study, is far, far younger than what we might have thought before the era of space probes.
The Neptunian moon, 7th largest in the solar system, joins Europa and Enceladus (left) as likely places for the existence of liquid water not too far from the surface.
At the temperatures one finds in the outer solar system, water is most often found as a hard crusty surface. Triton, for example, is about 400 degrees below zero.
At those temperatures, ice functions as rock does on Earth: it can get powdered into sand and dust by cratering, or on Titan, by weathering. Far below the surface, where tidal stresses increase the heat inside some of these moons, the ice can liquefy and erupt in volcanoes or geysers. Water equals lava for the cold outposts far from the sun.