Triton (moon)
During its 1989 flyby of Triton, Voyager 2 found surface temperatures of −235 °C and also discovered active geysers; Voyager 2 remains the only spacecraft to visit Triton. Triton is one of the few moons in the Solar System known to be geologically active (the others being Jupiter's Io and Europa, and Saturn's Enceladus and Titan). As a consequence, its surface is relatively young, with few obvious impact craters. Intricate cryovolcanic and tectonic terrains suggest a complex geological history. Part of its surface has geysers erupting sublimated nitrogen gas, contributing to a tenuous nitrogen atmosphere less than ​1⁄70,000 the pressure of Earth's atmosphere at sea level.
Triton (moon)-3