I consider space stations to be far more realistic than Mars colonisation, which to me seems like a destination that no-one would actually want to go to when th

I consider space stations to be far more realistic than Mars colonisation, which to me seems like a destination that no-one would actually want to go to when they realise that Mars has far lower gravity and far less sunlight than Earth - not to mention the hazards Martian dust. Even if we manage to terraform Mars, it'll still be a tough place to live. Space stations however - you can make them however you want. I've seen concepts of rotating habits that are so massive that there's no "roof" on the inner-side, only walls to stop the atmosphere leaking out. No idea if that would actually work or not, but it looked cool.