Just in case you are unfamiliar with the Jupiter System, maybe I better back up and describe it for you. If you check out Appendix I at the end of the book, you will notice that compared to the other bodies in the chart, Jupiter is big; I mean really big. Its circumference is more than the distance from Earth to Luna and its mass is greater than all the other planets and moons in the Solar System combined. Old Jove’s surface gravity is two and half times that of Earth and he has 63 moons. Of those moons, the four discovered by Galileo are the main ones and were given names from classical mythology by the astronomers of the 17th century: Io, Europa, Ganymede and Callisto. Then for a couple of hundred years they were called Jupiter I, II, III and IV, according to their order: from nearest to Jupiter to farthest. During the 20th century, the old classical names came back into use again, which suits me.
Excerpt from Chapter IV: Jupiter IV