Discovered 1865 Sept. 19 by C. H. F. Peters at Clinton.

Named after the daughter of the river god Inachus, son of Oceanus. She was changed into a heifer by Jupiter at the approach of Juno {see planet(3)} who saw through the deception and had her guarded by Argus who had a hundred eyes and slept with them closed only two at a time. The latter was killed by Mercury at Jupiter’s order and Io escaped through the Ionian Sea, named for her, to Egypt where some say she became Isis, the wife of Osiris {see planets(42) and(1923)}. (H 12)

The name Io has also been given to the first satellite of Jupiter, discovered 1610 by Galilei.