Triton Triton Voyager 2 Image Triton is about three-quarters the size of our own Moon, with a diameter of 2,700 km. The Voyager 2 space probe in 1989 showed that it has an icy surface of frozen nitrogen and methane which is pinkish in parts. Geysers of gas rise 8 km high from subsurface pockets of liquid nitrogen.
Triton is slightly bigger than the planet Pluto, which it is thought to resemble.
Probably Triton was once a separate body, like Pluto, but was captured by Neptune. Triton is gradually moving closer to Neptune, and will eventually be broken up by the planet's gravity. The Discovery of Neptune.