During the Fall, some habitats around the Jovian system were seized by everyone's favorite banana republic in space. Before they became the bioconservative dictators of the Sol System, I think a fun idea might be going into the specifics of the takeover and what came before as well.
-Before the Fall: Before the Fall, let's assume the Americans (or Pan Americans) have mostly developed this system. It's a nice strategic location, with reactor-grade helium and hydrogen in Jupiter. Stations (automated and manned) similar to Venusian aerostats may occupy the atmosphere, with some used for research and others for gathering the gases of value. The radiation of the planet is a big concern, so shielding is intensive. Europa's got some interesting research material, and the life under the icy crust might be a recent find. Researchers are moving in to special communities in Europa and in Jovian orbit, eager to get a sample of non-Earth organic samples. Perhaps a few asteroids and moonlets have been harvested and turned into habitats, automated factories, and shipyards. A few habitats may have larger than normal security forces, and maybe the Pan Americans have a few strategic outposts here to safeguard their investments.
-During the Fall: A few battered remnants of the Pan American forces fall back to the Jovian system after being ejected from Earth. Maybe dragging some refugees with them, they manage to arrive and set to work holding the lines. They seize every habitat they can, assimilating and drafting militias, hackers, and others to battle the TITAN menace (and perhaps crush unrest, rebellion, and the like as well). They coordinate with remaining Pan American (or perhaps any Earth bloc) vessels willing to join them. They purge "infected" structures and shipyards without a second thought, strong-arming their way into the Junta we all know and love/hate/loathe.
A few ideas for campaigns spring to mind:
--The PCs meet here during the Fall after fleeing Earth or elsewhere, and get conscripted by the Junta. Some of them are synthmorphs, and aren't appreciated.
--Someone is attacking Jovian aerostat stations and transports within the atmosphere. They are seizing supplies and killing all witnesses, often leaving no bodies and deleting sensor footage. Are these some sky pirates of Jupiter, guerrillas and rebels against the regime, or something more sinister?
--There's neutrino scans reveling strange artifacts (10 AF) under the atmosphere of Jupiter. Something is down there that was not before, deeper in than a regular structure should be. Is it a malfunctioning hab, shipwreck, or some horrific TITAN construct waiting in there?
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"Ipsa Scientia Potestas Est."