Thalassa is a moon of which planet?

Thalassa, also known as Neptune IV, is the second-innermost satellite of Neptune. Thalassa was named after sea goddess Thalassa, a daughter of Aether and Hemera from Greek mythology. "Thalassa" is also the Greek word for "sea". Thalassa was discovered sometime before mid-September 1989 from the images taken by the Voyager 2 probe.

Neptune is the eighth and farthest-known Solar planet from the Sun. In the Solar System, it is the fourth-largest planet by diameter, the third-most-massive planet, and the densest giant planet. It is named after the Roman god of the sea and has the astronomical symbol ♆, a stylised version of the god Neptune's trident.

Neptune has 14 moons, the latest discovered in 2013. Each of the moons is named for a mythological Greek water deity. Moving from closest to Neptune to furthest out, their names are Naiad, Thalassa, Despina, Galatea, Larissa, S/2004 N1 (which has yet to receive an official name), Proteus, Triton, Nereid, Halimede, Sao, Laomedeia, Psamathe, and Neso.