Voyage of the Jeanne d'Arc
Jupiter, once the most massive planet in the Sol system, was a massive gas giant with more than sixty moons and moonlets, and a gravitational field that pulled in debris and protected the inner planets from bombardment.
At some point in the ancient past, something happened to Jupiter. Scholars debate the nature of the event, some arguing that it was Demons, others that it was a natural function of astral activity, and still others that it was weapons testing. Whatever the case, Jupiter is now known as Hephaestus. A massive quantity of the gas giant's atmosphere was expelled outward, forming rings to rival Saturn. The remains of the planet itself are essentially a dwarf star, a blasted wasteland of nuclear fire.
People still live in the Hephaestus subsystem, most of them on the moons Ganymede, Callisto, Europa, and Io. The subsystem is dominated by the Bacarran Syndicate, a government born out of ancient labor unions opposed to the military domination of the Protectorate.