As of this time, Triton (a moon of Neptune) has the coldest temperature ever recorded in human history on any terrestrial surface… -235 C, -391 F. At these temperatures, nobody would have expected anything other than a huge frozen solid ice ball. Instead, Triton is littered with what we now call cryo-volcanos… or cold volcanos. They erupt or eject materials other than molten rock, such as water, ammonia or methane. As we are seeing in places like Titan (who is also suspected of having cryo-volcanos) many characteristics of Earth geology and weather are simulated elsewhere in the Solar System with different materials. On Earth it rains water, but on Titan it rains methane, and likewise on Triton it erupts probably liquid nitrogen instead of magma as it does here on Earth.
Only two active cryo-volcanos have been confirmed on Triton, but it is generally assumed that each one of those black smudges visible in this image are the remnants of recently active cryo-volcanos. There are quite a few…