Comment Re:Surface? (Score 1) 156
Develop a drilling or excavation machine that can operate mostly autonomously (ideally, using something like industrial lasers to avoid mechanical wear on the drilling apparatus) and send one or more to Mars several years/decades ahead of when you want to send the humans. Have them drill at a downward angle into the side of a crater, and once you've gone sufficiently far then start having them dig or drill to the side. Ideally, by the time the colonists reach Mars all they need to do is install airlocks at the entrances, pump in breathable air, and maybe knock down the (hopefully thin, by this point) walls between the side tunnels so you don't have to go outside to visit the neighbors. There may be some leaks but hopefully the colonists can make some sort of cement out of the Martian dirt to plug them.