Thalassa (moon)

Thalassa, also called Neptune IV, is the second-innermost moon of the planet Neptune. It orbits very close to Neptune, making it one of the smaller and quicker-moving moons in the planet's system.

The moon was named after Thalassa, a sea goddess from Greek mythology. Thalassa was believed to be the daughter of Aether and Hemera. In Greek, the word "Thalassa" simply means "sea," which fits well with its place near the giant, stormy planet Neptune.

Scientists discovered Thalassa in 1989 during a space mission that flew by Neptune. Studying moons like Thalassa helps us learn more about how planetary systems form and change over time.

Discovery

Thalassa was found before September 1989 using pictures from the Voyager 2 probe. It was given a temporary name, S/1989 N 5, and the finding was shared on September 29, 1989. The moon got its official name, Thalassa, on September 16, 1991.

Physical properties

Thalassa has an uneven shape and looks like it was put together from pieces after a big crash. Scientists think it formed from fragments of Neptune's early moons. These pieces were disturbed by Triton, one of Neptune's larger moons. Even though it has an unusual shape, Thalassa seems to be somewhat flat like a disk.

Orbit

Thalassa orbits below Neptune's synchronous orbit, so it is slowly moving closer to the planet. This might cause it to crash into Neptune's atmosphere or break apart to form a ring around the planet.

Thalassa and the moon Naiad have a special pattern in their orbits. Every about 21.5 days, Naiad passes above and below Thalassa twice, keeping their paths safe and stable. Even though they are close, this pattern helps them stay apart.