Neptune, the smallest of the gas giant planets, has the fewest number of known satellites of any outer planet. Neptune's moon system is dominated by Triton, which makes up about 99 percent of the satellite system's mass.
Neptune's Moon Triton
Triton was discovered in 1846 by William Lassell, just days after he discovered Neptune. Triton is more than 2700 kilometers in diameter, making it one of the largest satellites in the solar system. It is a bit smaller than Earth's moon. One of Triton's unique features is its retrograde orbit. A retrograde orbit is one in which the satellite orbits its parent planet in the opposite direction of the planet's rotation. This indicates that the moon did not form in conjunction with the planet but was captured later. Triton was most likely a Kuipter belt object before becoming a moon. Indeed, Triton is larger than Pluto, the best known Kuipter belt object, and the two objects are composed of the same elements.
Another unique feature of Triton is its liquid nitrogen geysers. Solar heating allows a portion of Triton's crust to warm enough to allow nitrogen gas below to escape. The geyser eruptions can last for as long as an Earth year. Triton is also know for its "cantaloupe" surface features. A portion of the planet is covered in cantaloupe terrain that has the pockmarked look of the skin of a melon. This interesting mottled texture has not been seen on any other planets or satellites. The image here shows the cantaloupe terrain in the upper portion of the satellite.
Neptune's Inner Moons
Inside Triton's orbit, between Neptune and its largest satellite, are six known moons. These moons are called regular satellites. They are named Naiad, Thalassa, Despina, Galatea, Larissa, and Proteus. These small moons were all discovered in the 1980s. Five of the six satellites were discovered by the Voyager 2 spacecraft as it flew past in 1989.
Neptune's satellite system is unusual in that Triton is the only large moon. The smaller, inner moons appear to be the remains of collisions of moons that existed before the capture of Triton. The addition of Triton to Neptune's orbit probably caused the early moon system to be disrupted with collisions that broke apart bodies until what remains are the inner moons seen today.
Neptune's Outer Moons
Outside the orbit of Triton lie six more satellites. The outer moons are named Nereid, Halimede, Sao, Laomedeia, Psamathe, and Neso. Of these, Halimede, Psamathe, and Neso are also in retrograde orbits, like Triton. These small moons were found in the early 2000s except for Nereid. Nereid is the largest outer moon and was discovered in 1949. Nereid was discovered by Gerard Kuiper, for whom the Kuiper belt is named. Nereid may once have been a Kuiper belt member that was captured by Neptune.
Source: NASA
Kelly Whitt - I have been a professional writer for more than a decade, covering many topics from science-based articles to do-it-yourself home ...
