To me, colonizing another planet is not about expanding or moving the human race somewhere else. It’s a backup plan. Right now, our entire species exists all on this one planet. There is a non-zero chance that we could all be eradicated in an instant by a sufficiently large asteroid or comet, or by nuclear war. There is no backup for the human race or any other species on earth. Once we have a colony, we greatly increase our likelihood of surviving the end of the world. I think that’s worth investing in, and we should bring as many species with us as possible. For all we know our planet may be the only oasis of life in the galaxy or even the universe. Didn’t you think we should have a backup?
Do we actually know how to build a self-sustaining colony? Last I heard, we still had fundamental science and engineering questions to be solved even if we suddenly had an unlimited budget.
Things that come to mind include building a sustainable closed ecosystem, figuring out a long-term power source (is there uranium on Mars? Nuclear reactors run for a long time, but we can’t rely on fresh fuel rods being shipped from Earth), and planning for enough industrial base that things like mining the necessary uranium, digging tunnels, housing construction, etc aren’t colony-ending problems.
