Long term this would be still easier to make really sustainable than mars mision.
1) Power:
- power can be from nuclear reactors similar like with nuclear submarines
- you can drill down near some geothermal water
- you can still deploy some floating solar panels with 200m cable linked to habitat and fold back similar like kite in case tsunami
- you can put habitat nearby some water currents (e.g. nearby some 2 underwater mountains/islands and you will have water current because of tidal waves) and deploy some power kite or hydro turbine
2) Oxygen + energy
- just make electrolysis on water molecule to get both oxygen and hydrogen
3)
- grow some seaweed food
- grow fishes and other sea food
Sure this is still hard to pull off but at least 1 order of magnitude easier than on mars. On earth you don't have to worry about gravity, lack of water, lack of geothermal power, radiation from space, protection from micro meteors, -73C temperature during the night on mars (deep water on earth even 200m below is not frozen but between 0-3C). Humanity after 10 years of living underwater can still try to go back to land after things gets better post asteroid impact.
Oh sure. Colonies on Mars are a complete fantasy right now. They start and end with Mars's lack of a magnetic field.
could we create a self-sufficient habitat underwater? Probably. But given that it would lack key abilities (heavy industry for example) it would inevitably decay (Probably quite quickly.)
1) Power:
- power can be from nuclear reactors similar like with nuclear submarines
- you can drill down near some geothermal water
- you can still deploy some floating solar panels with 200m cable linked to habitat and fold back similar like kite in case tsunami
- you can put habitat nearby some water currents (e.g. nearby some 2 underwater mountains/islands and you will have water current because of tidal waves) and deploy some power kite or hydro turbine
2) Oxygen + energy
- just make electrolysis on water molecule to get both oxygen and hydrogen
3)
- grow some seaweed food
- grow fishes and other sea food
Sure this is still hard to pull off but at least 1 order of magnitude easier than on mars. On earth you don't have to worry about gravity, lack of water, lack of geothermal power, radiation from space, protection from micro meteors, -73C temperature during the night on mars (deep water on earth even 200m below is not frozen but between 0-3C). Humanity after 10 years of living underwater can still try to go back to land after things gets better post asteroid impact.