Proteus, also known as Neptune VIII, is the second-largest Neptunian moon, and Neptune's largest inner satellite. Discovered by Voyager 2 spacecraft in 1989, it is named after Proteus, the shape-changing sea god of Greek mythology.  Proteus orbits Neptune in a nearly equatorial orbit at the distance of about 4.75 times the radius of Neptune's equator.   It is over 400 km in diameter and shaped like an irregular polyhedron with several slightly concave facets and relief as high as 20 km. Its surface is dark, neutral in color, and heavily cratered.  Proteus's largest crater is Pharos, which is more than 230 km in diameter.

Proteus

PDS Image Atlas

Cross-mission and cross-instrument searches for images and spectra from Cassini, Voyager 1 and 2, Galileo, New Horizons, and the Hubble Space Telescope