The Jovian system is a superior target for self-sustaining colonization. Quite a bunch of PF people (Nereid, all the mentors in earshot, and plenty of others) know the facts. It is a beautiful and interesting system consisting of a variety of different moon-size objects within comparatively easy reach of each other. Trips between Jovian moons take only a few days. One key fact is the availability of reaction mass for propulsion. Europa has a thick ice shell covering its liquid water oceanic layer. Missions to the Jovian system might be equipped to take on reaction mass (water or liquid hydrogen) at Europa. Europa ice is estimated to be many kilometers thick. A colony with abundant nuclear electric generating capacity could hollow out habitats in the ice, far enough below the surface to be structurally secure. Other moons such as Ganymede and Callisto look interesting too, and appear to have water ice. Presumably the ice on Europa is rocky---has minerals mixed in with it. It should not be too difficult to design a chemical plant to extract the raw materials for civilization. Personally I would not want to go anywhere as dry and barren as mars and the moon----though mars has some lovely desert landforms, shaped in part by wind. Natural beauty is important and the spectacular thing Europa has is a sky with the planet Jupiter in it. Jupiter diameter is 143 thousand km and the distance from Europa is 671 thousand km. This means the angular width of jupiter is about 12 degrees. Compare this with the full moon seen from Earth which is 1/2 degree wide. We are talking about a gorgeous planet 20 times wider than the full moon is in our sky. 400 times bigger in angular area, than the full moon. With more colors and cloudforms to make it interesting. This is a very romantic sight. Humans living in the ice-caves of Europa would probably go to the surface for their honeymoons. They might even reproduce prolifically because watching Jupiter and the other Jovian moons is so romantic. Films made at Europa might have a good boxoffice on Earth. The Jovian system would be a fun place to inhabit for many reasons, including the fact that the trip from one "planet" to the next takes only a couple of days. Each Jovian moon goes around the primary in a few days or a week. So transfer orbits have similar periods. In the Solar system trips between planets take on the order of years, whereas in the Jovian system trips take on the order of days. Plus reaction mass for propulsion is available in a not-very-deep gravity well. Energetically, water at Europa's surface is a lot more accessible than water at the Earth's surface. So as a supplier of propellant it is a good bargain to switch over from Earth to Europa. I do not like the "moon-mars" initiative which seems to me a bad investment and destructive of human aspirations.