Jupiter is the fifth planet from Sol and the largest planet in the Sol system. Although it is a gas giant, its moons are the home of approximately forty-five million inhabitants. It is the closest of the outer planets, and is de jure governed by the United Nations and the Martian Congressional Republic.
- Ganymede, largest of Jupiter's moons, one of the largest system bodies without a substantial atmosphere, and whose domes are known as the "breadbasket of the Belt".
- Callisto, second largest and tidally locked with Jupiter, is about half ice (mostly water and some volatiles) with a likely metal and rock core. It is a key strategic point in the Belt, since it has both MCRN and UNN shipyards.
- Io, third largest moon, most geologically active object in the system with a high density, silicate rock crust, and an abundance of sulfur compounds. It hosts an inactive Helium-3 refinery.
- Europa, fourth largest, primarily made of silicate rock, has a water-ice crust, and probably an iron–nickel core with a very thin atmosphere, composed primarily of oxygen.