In our solar system, Europa has the highest potential for alien life based on what I've read. If Mars or moon had any, then they are possibly fossilized by now. Jupiter's environment seems like it would be faaaar fetched, however Europa does seem to have a conducive environment under ice. We need faster travel and generational discipline to get there, drill a hole, and send back data. Or something like a neutrino scanner that can pass through the ice and tell us like X rays if there is moving/wiggling objects in there. We're just now starting to even understand neutrinos, building something with it is still too futuristic. So that leaves us with just more patience… for now.
But how cool would it be to know there is life elsewhere within our lifetime! Sigh.