of the four galilean moons which is the closest to jupiter
Galilean moons Io (Jupiter I) is the innermost of the four Galilean moons of Jupiter and, with a diameter of 3642Â kilometers, the fourth-largest moon in the Solar System. It was named after Io, a priestess of Hera who became one of the lovers of Zeus. Nevertheless, it was simply referred to as "Jupiter I", or "The first satellite of Jupiter", until the mid-20th century.[11]