If scientists are unable to develop faster than light or wormhole technology by the 22nd Century, humanity may find themselves using gravitational assistance in order to travel throughout our solar system.
But in order to reach these distant gas giants alive (or at least moderately healthy), humanity may need a way station to resupply on food, supplies and oxygen.
Since the Jovian king (aka Jupiter) has been frequently used to fling satellites across the gulf of space, establishing a colony inside its domain may be the next logical step for conquering the outer solar system–with Callisto being the key.
Callisto orbits its Jovian parent at a distance of almost 2 million kilometers. Unlike its bigger brother Ganymede, Callisto lacks a well defined magnetic field, having to instead rely upon “daddy Jupiter” for protection.
Orbiting well beyond the wrath of Jupiter’s radiation belts, Callisto lies in a relatively quiet radio zone. With its surface lacking some of the more “interesting” features such as volcano’s and enormous mountain ranges, this tranquil world provide a stable (and safe) habitat for future colonists. Callistian residents would also be in the position to settle Ganymede, as well as establish scientific outposts upon the ice world Europa.
Callisto also harbors water and CO2 ice upon its surface, which would enable future colonies to not only grow food and create fuel for not only themselves, but also for way faring space travelers. This would allow future explorers to easily replenish their supplies, and then use Jupiter’s gravity to slingshot towards other planetary systems.
Having a similar scenario as Mars, Callisto’s location in the solar system would enable this lunar world to establish itself as an interplanetary pit stop, ensuring a vital economy based mainly on trade instead of vital resources.
Conquering this heavily cratered moon would provide yet another stepping stone for humanity, allowing our species to slowly (but surely) spread our population throughout our “tiny” star system.