TRITON:
       Neptune has eight moons. Triton is Neptune's largest satellite, with a radius of 1350 kilometer. This is three fourth the size of our Earth's moon. Discovered by Lassell in 1846, Triton has an unusual type of orbit around Neptune. It orbits its planet in the opposite direction of the way the planet spins, which leads scientists to believe that Triton formed independently of Neptune in the outer solar system and was later "captured" by the planet's gravity. Scientific evidence shows that the surface of Triton has a thin methane atmosphere. There is also a layer of ice covering the surface which may be frozen nitrogen. Another unusual characteristic of this moon is its appearance. There are large crater like features. However, these craters, instead of being formed by outside material hitting the planet at random, are all the same size and shape. This leads scientists to believe that these craters are evidence of something going on inside the moon itself. In addition to these craters, there are dark plumes or geysers, which are formed when sunlight warms the material beneath the frozen nitrogen, causing it to vaporize and burst out through the ice. Triton has the coldest temperatures in the solar system (it is currently farther out from the sun than Pluto), with a surface temperature of -235° C (-391° F). The atmospheric pressure at Triton's surface is about 15 microbars.

top...

NEREID:
       Nereid, with a radius of 170 km, was discovered by Kuiper in 1949. Although it encircles Nepune in a prograde orbit, it is very eccentric and inclined. In addition, Nereid also has a strange shape as well as surface in comparison to other satellites. Scientists have tried to determine the spin rate of this moon but have reached several contradictory results. It seems that either this moon has a dark spot on its surface or that it is irregularly shaped and is tumbling chaotically similar to Hyperion, Saturn's moon.

top...

NAIAD:
       Naiad was the last of Neptune's satellites to be discovered. It's diameter is 54 km and it's orbital period is 7 hours and 6 minutes at a distance of 23,200 km from Neptune. Naiad is oddly shaped and circles Neptune in the same direction as the planet rotates. Naiad was discovered by Voyager 2 in 1989. It's mass is unknown but it's equatorial radius is 29 km. The average distance from Neptune is 48,000 km long. Naiad's orbital period is only 0.294396 days. The magnitude is 24.7 Vo.

top...

THALASSA:
       Another of Neptune's moons is Thalassa. Thalassa is about 80 km in diameter. It's orbital period is 7 hours, 30 minutes and is at a distance of 25,200 km from Neptune. This satellite is irregularly shaped. Thalassa circles the planet in the same direction as Neptune rotates. Thalassa was discovered by Voyager 2 in 1989. It's mass remains unknown, but its equatorial radius is 40 km. Its average distance from Neptune is 50,000 km. The orbital period for Thalassa is only 0.311485 days. Thalassa has a magnitude of 23.8 Vo.

top...