A chapter of category E — speculation, marked as such. The question it asks is not whether we can leave, but who we would be when we arrived.
Two claims must be separated carefully, because they are routinely confused in public conversation.
What is established. Mars is cold, its atmosphere is thin and predominantly carbon dioxide, it lacks a global magnetic field and a breathable atmosphere, and its surface receives radiation levels hazardous to human tissue over long exposure. Robotic exploration has been remarkably successful; human settlement remains an unsolved engineering problem of the first order. Nothing about it is close.
What is speculation. Everything else — timelines, terraforming, self-sustaining colonies. I include this chapter not to make predictions but because the ethics of expansion are worth thinking through now, while the thinking is still free.