Discovered in 1846, Triton is the largest moon of Neptune - but it’s unlike any other. Scientists believe it was once a free-floating planet before Neptune’s gravity captured it.

Ganymede, Jupiter's largest moon and the solar system's largest, is bigger than Mercury and the dwarf planet Pluto, with a diameter of 5,268 kilometers.

A global color mosaic shows Neptune’s largest moon, Triton, from images taken by the Voyager 2 spacecraft in August 1989. HELSINKI — China is charting a long-term deep space strategy centered ...