in Greek mythology, daughter of the river god Inachus, she was pursued by Zeus and consequently changed into a heifer. The Jovian moon was discovered in 1610 and named for her by Galileo.
| Io (ī'ō, ē'ō) One of the four brightest satellites of Jupiter and the fifth in distance from the planet. It was first sighted by Galileo. See Note at moon. |