Main Page | See live article | Alphabetical index Larissa (or Larisa) is the fifth of Neptune's known moonss. It was discovered by Harold Reitsema based on ground-based stellar occultation observations, and was photographed by Voyager 2 in 1989. Larissa is irregular (non-spherical) in shape and appears to be heavily cratered, with no sign of any geological modification. Little else is known about it. Since its orbit is below Neptune's synchronous orbit radius it is slowly decaying due to tidal forces and will one day break up into a planetary ring or impact on Neptune's surface. Orbital radius: 73,600 km Diameter: 193 km (208 × 178) Mass: Unknown Orbital period: 0.554654 days Orbital inclination: 0.20° This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.