Proteus aka Neptune VIII is the second largest satellite of Neptune behind Triton. Also the largest non-spherical object in the Solar System. Named after a sea god from ancient greek mythology
The only colored photo, also by Voyager 2
Proteus was found on images taken by Voyager 2 in 1989, when it was passing by Neptune. It got the provisional designation S/1989 N 1
The discovery was announced on 7 July 1989. Stephen Synnott and Bradford Smith said it was viewed on 17 images taken over 21 days.
The name Proteus was given on 16 September 1991.
Its size is 440x416x404 km. Its larger than Nereid, another satellite of Neptune, however couldnt be found by telescopes because it was too close to the planet, blending with Neptune.
Its surface is covered with craters with one (Pharos) having an official name, this crater serves as the reference point for coordinates on the moon.
Proteus shows no signs of geological activity. Scientists say eventually Proteus will become round from its own gravity, because for example Mimas is less massive than Proteus but is round.