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Proteus is the second largest moon of Neptune, and the largest inner satellite. Despite the size of Proteus, it′s shape is quite irregular more like an irregular phoyhedron with several slightly concave facets and relief as high as 12 miles. The surface of Proteus is very dark, neutral in color, heavily cratered and does not reflect much sunlight, only about six percent of what is receives. The largest crater on Proteus is Pharos which is more than 140 miles in diameter.
Proteus is tidally locked with Neptune and rotates synchronously with its orbital motion and has one side always facing Neptune.
It is believed that Proteus is not an original body that formed with Neptune, but may have been part of the debris that was with Triton when it was captured.
Facts about Proteus
Discovered by: Voyager 2 Spacecraft
Date of Discovered: 1989
Planet Orbital Position: 7
Equatorial Diameter: 266 miles
Average distance from Planet: 73,310 miles
Axil Tilt to orbit: 0 °
Inclination to Neptune equator: 0.524 °
Rotation Period: 1.122 days
Orbit Period: 1.122 days
Surface Temperature: -368 ° F.
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