Seeing the first person to spell subtle with a b

kinda, dark energy is the unknown explanation for the expansion of the universe. Once we understand it enough to know what it is responsible for it’ll no longer be dark.

I think you missed my point, I don’t believe we have a self sustaining population on earth (yet)

I don’t disagree that having a self sustaining population of humans somewhere other than earth will be an important milestone.

But a much more pressing milestone is a the first self sufficient population, which I don’t see mars supporting