Other names put forward , but the names which eventually prevailed were chosen by Simon Marius . Marius claimed to have found the moons at the same time as Galileo : he named them after lovers of the god Zeus ( the Greek equivalent of Jupiter ) : Io , Europa , Ganymede and Callisto , in his Mundus Jovialis , published in 1614 . The names that eventually prevailed were chosen by Simon Marius , who claimed to have discovered the moons at the same time as Galileo : he named them after lovers of the god Zeus ( the Greek equivalent of Jupiter ) : Io , Europa , Ganymede and Callisto , in his Mundus Jovialis , published in 1614 .