Proteus

Proteus was discovered during the Voyager 2 spacecraft's flyby of the planet in July 1989. Named after the shape-shifting sea god of Greek mythology, Proteus stands as the second-largest moon around Neptune, surpassed only by Triton. It possesses an estimated diameter of approximately 420 kilometers, dwarfing many other moons in the Neptunian system. With an irregular, elongated shape and heavily cratered surface, Proteus reflects its ancient age and the countless impacts it has endured. Its most distinctive feature is the immense "Pharos" crater, spanning over 200 kilometers. Proteus orbits Neptune at an average distance of about 117,647 kilometers and has an orbital period of approximately 26 hours and 54 minutes. Believed to be a captured object, it may have originated from the Kuiper Belt or the asteroid belt.