Near-Jupiter space is controlled by the Jovian League, a federation of the small colonies on Ganymede and Callisto, and the outpost on Europa. Each of these colonies is a nation-state; the League itself is a loose association.
The largest and most massive planet, Jupiter orbits at a mean distance of 5.203 AU (43 light minutes). The atmosphere of the giant planet is the source of most of the helium-3 burned in Belter ships. The gas is collected by robotic mines that float beneath the roiling banks of clouds.
All four of the Galilean moons are tidally locked to Jupiter. Ganymede, Callisto and Europa are all icy bodies, so the colonies are heavily dependent on mining Io and the rocky outer moons for resources. The most heavily exploited of these small worlds is Himalia.
The moon, a body larger than Luna, is utterly unlike any other object in Sol System. Volcanos, lava-flows and lakes of bright orange molten sulphur dominate the surface of Io. There are extensive regions frosted with sulphur dioxide snow.
Io's orbit lies within Jupiter's radiation belts, making it inimical to life, but it hosts automated mines and research centres. There has been considerable interest recently in the possibility of tapping the energy of the Io flux tube.
Europa, the third largest of the four Galilean moons, is slightly smaller than Luna. Its surface is a very smooth icesheet, as thick as 100km in places, marked by bright or dark linea and low, scalloped ridges. On the nearside Jupiter dominates the sky, appearing to have a diameter 24 times that of Luna as seen from Earth.
The research outpost on Europa is dedicated to the study of the complex organic reactions and pseudolife that is found around volcanic vents on the floor of the ocean that lies beneath the planetwide ice-sheet. The Europan pseudolife consists of self-replicating molecules, making up an ecosystem very like the system of RNA replicators postulated to be the earliest stage of life on Earth. Europa Station is nominally a Praesidial installation, leased by Earth from the League. Despite this, it is dominated by biochemists and xenobiologists from the Amazonis Planitia Institute for Biological Sciences on Mars.
The largest of the Galilean moons, Ganymede is a world larger than the planet Mercury. The icy surface is divided into dark regions mingled with younger brighter areas scoured by grooves and furrows with kilometer-high sides.
Ganymede is the capital of the Jovian League, and the most populous of the Galilean moons. The moon is has two nation states, former colonies of Greater Azanian and Australia.
This world, the second largest of the Galileans, is the most heavily cratered in Sol System, marked everywhere by shallow impact basins. The dirty ice of the crust is pocked by myriads of craters, the largest of which are the huge ringed basins of Valhalla and Asgard. The Callistan towns are predominantly Han Chinese.
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