Proteus (moon)

Proteus (moon)

Proteus ( /ˈproʊtiːəs/; Greek: Πρωτεύς), 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 circles Neptune in a nearly equatorial orbit at the distance of about 4.75 equatorial radii of the planet.

Despite being more than 400 km in diameter Proteus has a somewhat irregular shape with several slightly concave facets and relief as high as 20 km. Its surface is dark, neutral in color and heavily cratered. The largest crater is more than 200 km in diameter. There are also a number of scarps, grooves and valleys related to large craters.

Proteus is probably not an original body that formed with Neptune; it may have accreted later from the debris created when the largest Neptunian satellite Triton was captured.