Other Moons of Neptune - The Solar System on Sea and Sky
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Proteus
Proteus [PROH-tee-us] is the sixth of Neptune's moons and is the second largest. It was named after a mythical sea god who could change his shape at will. Proteus was discovered in 1989 by the Voyager 2 spacecraft. It is irregular in shape and is probably about as large as an irregular body can be before gravity pulls it into a spherical shape. Like Saturn's moon, Phoebe, Proteus is extremely dark in color. It reflects only 6% of the sunlight that strikes it. Proteus is larger than Nereid, but was discovered much later because it is so dark and so close to Neptune that it is difficult to spot in the planet's bright glare. Its surface is heavily cratered, and shows no signs of geologic activity.
Voyager 2 Image of Proteus
(NASA / JPL)
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Nereid
Nereid [NEER-ee-ed] is the eighth and outermost of Neptune's moons and is the third largest. It was named after the sea nymphs who were the daughters of Nereus and Doris. Nereid was discovered by Gerard Kuiper in 1949. It reflects about 14% of the sunlight that strikes it. This makes it a little brighter than Earth's moon and more than twice as reflective than Proteus. Nereid is famous for having the most eccentric orbit of any moon in the Solar System. Its distance from Neptune ranges from 841,100 miles (1,353,600 km) to 5,980,200 miles (9,623,700 km). This odd orbit suggests to some astronomers that Nereid may be a captured asteroid or Kuiper Belt object. Not much else is known about this moon.
Voyager 2 Image of Nereid
(NASA / JPL)