Space · Moons
Larissa
A moon of Neptune — An inner Neptunian moon — observed in a 1981 occultation before formal discovery.
Quick facts
Parent planet
Diameter (mean)
194 km
Mass
4.9 × 10¹⁸ kg
6.67e-05 Moon masses
Mean orbital radius
73,548 km
Orbital period
0.555 Earth days
Discovery year
1989
Discoverer
Voyager 2 imaging team (Harold Reitsema observed 1981)
Naming origin
Nymph, lover of Poseidon
Surface conditions
Larissa is an irregular inner moon of Neptune, 194×184×162 km. The surface is dark and heavily cratered. Voyager 2 confirmed the moon's existence in 1989; Harold Reitsema and others had observed a brief stellar occultation in 1981 consistent with a body near this orbit, retrospectively credited as the first observation.
Missions and observations
Every Neptune-system mission has had an opportunity to image or characterize Larissa. The list below is the Neptune-system mission catalog; specific Larissa encounters are documented in mission archives.
| Mission | Year at Neptune | Status |
|---|---|---|
|
Voyager 2 NASA |
1989 | Completed |
Naming etymology
Larissa was a nymph in Greek mythology, a lover of Poseidon (Neptune's Greek equivalent) and the namesake of the Greek city. 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.