[koide]

I'm not convinced. After all, colonization of far away lands has been done throughout history and in many cases the return trip was as hard as it would be on Mars.

I picture the confinement problem as the most troublesome, but astronauts spend months in orders of magnitude tighter spaces and surviving in relatively good condition.

There's no reason at all you should send untrained people on those first missions and there's also no reason at all not to schedule yearly trips to bring back the people who couldn't stand the pressure.

Now, of course it will be insanely hard, there will be highly complex issues with no apparent solution that will have to be solved via improvisation without the proper means. But humans seem to have done it again and again.