 The Voyager missions vastly improved our understanding of the Galilean moons , and also discovered Jupiter 's rings . They also took the first close @-@ up images of the planet 's atmosphere , revealing the Great Red Spot as a complex storm moving in a counter @-@ clockwise direction . Other smaller storms and <unk> were found throughout the banded clouds ( see animation on the right ) . Two new , small satellites , <unk> and <unk> , were discovered orbiting just outside the ring , making them the first of Jupiter 's moons to be identified by a spacecraft . A third new satellite , <unk> , was discovered between the orbits of Amalthea and Io . 
