**Titan’s** ocean is far deeper beneath very thick ice (better for a surface base than a subsea one), and **Ganymede’s** ocean is likely sandwiched by high-pressure ices that isolate it from rock—bad for tapping seafloor energy. Compared with Mars, Enceladus is harder to reach and resupply (longer travel times, extreme low-g health issues), but once bootstrapped underwater it could be **more self-sustaining** in power and shielding than a Martian surface outpost.