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 several had central circular hearths. Narrow lanes separated houses. A great profusion of unlined pits ("bothroi") was characteristic of this phase: eventually they became filled with waste matter, bones, potsherds, even whole pots. The pottery, markedly discontinuous with Lerna III, shows a range of new forms, and the first signs— regular spiral grooves in bases and parallel incised lines— marking the increasing use of the potter's wheel. Painted linear decoration in dark glaze on the pale body is characteristic of Lerna IV. Caskey identified early examples of the ware that in Middle Helladic contexts would be recognized as Minyan ware,