Earth is by far the best we can get, but on big enough spaceships it is possible to create living conditions that are better than on any other body of the Solar

Earth is by far the best we can get, but on big enough spaceships it is possible to create living conditions that are better than on any other body of the Solar System, except perhaps on a ship floating in the clouds of Venus. The experiments done on ISS suggest that for optimum health a gravity of at least two thirds of that of Earth is necessary, which disqualifies almost all the bodies from the Solar System, because they are either too small or too big. On a rotating spaceship it is possible to create any level of artificial gravity. In theory, one could make an underground rotating living space on Mars, to increase the apparent gravity, but that would consume much more energy and it would complicate entering and exiting, in comparison with a rotating spaceship. Obviously, something like this will not be built any time soon, but nonetheless an expansion into the Solar System is possible even without living on the surfaces of other celestial bodies.