Quick facts
Parent planet
Diameter (mean)
82 km
Mass
3.75 × 10¹⁷ kg
5.1e-06 Moon masses
Mean orbital radius
50,074 km
Orbital period
0.311 Earth days
Discovery year
1989
Discoverer
Voyager 2 imaging team
Naming origin
Primordial Greek goddess of the sea
Surface conditions
Thalassa is the second-innermost moon of Neptune, just outside Naiad. Like Naiad, it is dark, small, and orbits inside the synchronous orbit, slowly spiraling inward.
Missions and observations
Every Neptune-system mission has had an opportunity to image or characterize Thalassa. The list below is the Neptune-system mission catalog; specific Thalassa encounters are documented in mission archives.
| Mission | Year at Neptune | Status |
|---|---|---|
|
Voyager 2 NASA |
1989 | Completed |
Naming etymology
Thalassa was the primordial Greek goddess of the sea, daughter of Aether and Hemera. Adopted by the IAU in 1991.
Methodology & sources
Diameter, mass, and orbital parameters from JPL Solar System Dynamics — Physical Parameters. Discovery year and discoverer from the JPL Satellite Discovery Circumstances. Naming etymology from the IAU Working Group for Planetary System Nomenclature. Stylized SVG hero composed from NASA / JPL imagery as visual reference; no photographs are reproduced.