NASA Voyager 1 Launch

Simply put, resistance to the creation of a space frontier originates with the insecurities of Western leaders. First, it is clear that everything changes with the emergence of a frontier. Established power structures are usually shaken, not reinforced. (If this is not clear, try reading Walter Prescott Webb's The Great Frontier, particularly the last chapter, and Divided We Stand: The Crisis of a Frontierless Democracy, by the same author.) Europa: Planetary scientists generally think that a layer of liquid water swirls around beneath Europa's surface, and that heat from tidal flexing causes the subsurface ocean to remain liquid. It is estimated that the outer crust of solid ice is about 6 to 19 miles thick, including a ductile "warm ice" layer that hints that the liquid ocean underneath may be 60 miles deep. This means that Europa's oceans would amount to slightly more than two times the volume of Earth's oceans. Titan orbits Saturn once every 15 days and 22 hours. Like Earth's large Moon, in addition to many other moons in our Solar System, Titan's rotational period is precisely the same as its orbital period. This means that Titan only shows one face to its parent-planet, while the other face is always turned away.