About Proteus
Proteus is Neptune’s second-most-massive moon — too dark to have been seen from Earth, it was discovered only when Voyager 2 flew past Neptune in 1989. Its irregular, heavily cratered shape and very low albedo (~10%) suggest a primitive, carbon-rich body that survived the disruption caused by Triton’s capture.
Physical Properties
Orbit
Gallery
Hand-picked mission imagery of Proteus sourced from NASA and partner archives. Click any photo for full resolution and source attribution.
Imagery on this page is provided by the original mission teams. Full attribution terms: Image Rights & Credits.
Sources & Further Reading
- NASA — official mission / factsheet page
- Wikipedia — extensive cross-referenced article
- NASA u2014 Proteus
Numerical values (radius, mass, orbital elements, temperatures) are drawn from NASA NSSDC Planetary Fact Sheets, JPL Horizons, and the JPL Small-Body Database. Last refreshed: 2026-06-08 01:37:02.