Proteus (satellite)

Proteus is the second-largest moon of Neptune. Discovered in 1989 by the Voyager 2 spacecraft, it is an irregularly shaped body with a mean radius of approximately 210 kilometers (130 miles). Proteus orbits Neptune at a distance of about 117,647 kilometers (73,000 miles), lying within Neptune's ring system.

Proteus is dark and heavily cratered, indicating an ancient surface. Its low albedo (reflectivity) suggests that it is composed of materials similar to those found in other dark, icy bodies in the outer solar system. The largest identified crater on Proteus is Pharos, which is approximately 230-260 kilometers in diameter.

Unlike many of the larger moons in the solar system, Proteus is not tidally locked, meaning that it does not always show the same face to Neptune. However, its rotation is synchronous, meaning its orbital period matches its rotational period.

The origin of Proteus is still debated. It is believed to be a captured object or formed from debris resulting from a major impact on a larger Neptunian moon. Its irregular shape suggests that it lacks sufficient self-gravitation to pull itself into a sphere.

Further exploration of Proteus would be required to determine its precise composition, formation, and geological history.