The assumption appears to be "one" Mars habitat, with a lot of engineered systems to support human (and other) life. Three would be better, and each should be

The assumption appears to be "one" Mars habitat, with a lot of engineered systems to support human (and other) life. Three would be better, and each should be capable of supporting the population of one of the others (that is, meaningfully under-utilized.) When, not if, a biosphere breaks down the inhabitants will have a safe refuge. Meanwhile the under-utilized biosphere can hoard, ummm, accumulate, spare food and water for use in lesser emergencies.