On August 25, 1989, NASA's Voyager 2 probe flew past Neptune, the farthest planet from the sun in our solar system, and Triton, the largest of Neptune's 13 moons. The footage the craft filmed has recently been restored and shows off Triton's strange surface in great detail. According to NASA,
The new Triton map has a resolution of 1970 feet (600 meters) per pixel. The colors have been enhanced to bring out contrast but are a close approximation to Triton's natural colors. Voyager's "eyes" saw in colors slightly different from human eyes, and this map was produced using orange, green and blue filter images. In 1989, most of the northern hemisphere was in darkness and unseen by Voyager. Because of the speed of Voyager's visit and the slow rotation of Triton, only one hemisphere was seen clearly at close distance. The rest of the surface was either in darkness or seen as blurry markings.
Voyager 2—the only spacecraft to fly past Neptune and Triton—discovered a number of things about the moon as it sailed past. The moon's surface temperature is -391°F, making Triton one of the coolest things in our solar system. Triton's surface also has active geysers, one just a few geologically active moons (including Jupiter's Io) in our solar system. You can see a photomosaic of Triton's surface here.