re: Humans are tough and versatile
"But what about a years-long trip to and from Mars? Or a generations-long voyage to the stars?"
We do what we have always done- learn how to adapt to a new environment.
We learn from trying; we learn form studying; we learn from doing. We evolve. We progress. We adapt. We learn.
That is how we went to the Moon. That is how we have progressed through time. That is how we have gone from a bunch of primative animals to a race that can leave the Earth.
What was impossible yesterday is possible today.