Earlier quoted context omitted.
Or you're a space explorer, at the very edge of civilization and technology, pushing the human race forward and signing your name in history for the next thousand years.
but it's not really pushing anything, it's just a huge waste of money that would be better spent on developing technologies for extra-solar system travel. People living on a dead planet serves no purpose, it doesn't even increase the species potential for surviving cataclysmic events, because without an earth bases resupply any martian colony will be soon dead. Build spaceships that people can live on and head out of…
Physically getting to Mars and setting up camp is a challenge. Physically getting to another solar system and setting up camp is a challenge to the power of challenge. The numbers and difficulties are profoundly greater between the two.
Self sufficiency is entirely possible given enough energy, material, and care. We've managed to do it for four billion years on this planet. There's no reason it can't be done on another planet, or a ship as you mention.
I maintain that creating a stable-enough social structure that can survive offworld long-term seems to be most difficult part of the quest to leave Earth.