Hydra (moon) the Hydra, the nine-headed serpent that battled Heracles in Greek mythology. The nine heads of Hydra are a reference to Pluto's tenure as the ninth planet; its initial, "H", refers to the Hubble Telescope, which discovered Hydra and, together with Nix, to the "New Horizons" mission whose safe passage was the motivation for taking the Hubble images. Hydra orbits the barycenter of the system in the same plane as Charon and Nix, at a distance of about 65,000 km. Its eccentricity of 0.0059 is small, but significantly non-zero, and the largest of those of Pluto's small moons (slightly larger than
Lerna vanished sacred Lake Lerna, which was a freshwater lagoon, separated by barrier dunes from the Aegean. In the Early Bronze Age Lake Lerna had an estimated diameter of 4.7 km. Deforestation increased the rate of silt deposits and the lake became a malarial marsh, of which the last remnants were drained in the nineteenth century. The name Lerna is suggested to be connected with the Hattic plural prefix le- plus arinna, arna 'spring', 'pool', 'well', 'source'. Lerna In classical Greece, Lerna () was a region of springs and a former lake near the east coast of the Peloponnesus, south of