E) Jupiter

Once considered fertile ground for colonization, Jupiter was largely abandoned as a target for development for a variety of reasons - Jupiter's gravity and violent atmosphere negate the possibility of exploiting its atmosphere, while its unimaginably powerful radiation belts would be lethal for anyone venturing to most of the more interesting moons. This remains as true in 2500 as it was in prior centuries. Despite these factors, humans can be found in abundance around Jupiter. Drawn by the resources and the open spaces, Jovian space represents a frontier of sorts, a place of frequent clashes between the space-going powers of the Solar System.Io could be a treasure-trove of exploitable elements, such as sulfur compounds. Unfortunately it is deep in Jupiter's magnetosphere, and receives radiation too powerful for the all but the strongest shields. Likewise, the surface of Io is hellish; unstable and constantly changing, it presents a challenging environment. Other than a few robotic mining operations and the unfortunate technicians who monitor them, there are no humans on Io's surface.

Europa was settled originally by an infamous group of Wild Belters who claimed it as their own, who called themselves the Lords of Europa. Drawn by its endless supplies of water and other elements difficult to find on asteroids, they stayed because it offered them security and distance. Since that time, Europa has become a magnet for outcasts and criminals from all over the Solar System. About one million people live in various submerged habitats (from small family habitats to full towns) in a state of semi-anarchy, sheltered from lethal Jovian radiation by miles of ice. Though they claim all of Jupiter as their own, they tend to remain on their moon, living free by hiding in Europa's omnipresent ocean. Europa is known throughout the Solar System as the place where anything can be had or done, for a price. The only real unbreakable law is "The Deal", the idea that a deal once agreed to must be upheld. This ideal is enforced by threat of violence and by reputation, meaning it is more of a guideline than a hard rule. Europa has no real navy, but there are a large number of pirates, the only true pirates in the Solar System. They hide their vessels in deep cracks in the icy crust, where the ice is thin enough to be blasted open with missiles. They then lie in wait, hiding from patrolling Saturnian warships. These pirates are a vital part of the Europan economy, so nobody ever asks them where they get their wares.

Ganymede is an icy moon which receives a strong dose of radiation from Jupiter's magnetosphere, but not nearly as much as Europa. In theory this makes it open real estate, but there is little of interest on the moon that cannot be had elsewhere. The lack of significant useful resources means that none of the planetary states has any real interest in the moon. There are no large human settlements on Ganymede , but there are several smaller outposts inhabited by those seeking isolation. There are a couple of Christian monasteries, established by refugees from Mars. These monasteries are largely left alone, even by Europan pirates, and they serve as places of sanctuary and refuge. Callisto is similar to Ganymede, an icy moon that orbits further out than the other three moons. It suffers relatively little radiation from Jupiter, and the surface has some useful quantities of exploitable minerals. As a result, Callisto has been settled by several groups. Numerous small habitats, settled by homesteaders from Saturn, the Belt League, the Triton Republic, Europa, and even Chandra work the surface. Many of these habitats, each housing only a few hundred people, are heavily armed - range wars are common, as are raids from Europa and Wild Belters.