[DanielBMarkham]

I'm not sure of the exact amount, but water can be used for shielding.

So maybe we end up with huge domes made of tanks with 20' of water in them.

Also, since Mars has CO2, I'm guessing once a dome is up, we simply pressurize it with the surrounding atmosphere? Once pressurized we could use O2 tanks and cannulas, or add plants?

I fear that there is going to be a huge political debate first -- a lot of folks are going to say that man isn't worthy/able/competent/etc to colonize another planet.