It's now technically possible to start settlements/colonies/whatever in places where they've never been feasible before for lack of fresh water- check out the "watermakers" (reverse-osmosis desalinators) sold to yachtsmen today. Sailboats use them to cut water storage requirements in half (safely) on ocean voyages. Some are amazingly efficient- it should be possible to power one with two or three square yards of solar panels in the tropics. That would provide enough water for drinking- not enough for luxury. The system scales up easily- not cheaply.<br><br>On the other hand, you would be staking your life on very high tech equipment, presumably a long way from anywhere. Sounds like you have a lot more research to do.