Mars should be colonized, not the moon.

Plasma rockets? And these cost less how? You've just multiplied the cost of this endeavor to cut the trip down a few days. Making it overall even less cost effective an option. (I'll look into actual figures and include them in the next round) I think its safe to say that will be more costly an option than its worth at this point. But hell, so is colonizing at all at this point, so hypothetical are fine I suppose. Gravity The weight relation of objects to that of earth is more applicable since the structures and machinery that we are transporting to these places are built here. Comparing the ratios to earth is more accurate. Comparing the moon and mars directly is misleading when the gravity is already on a much smaller scale than earth. Ex. Gravity is .01 of earths and another is .02 of earths. You could make your same 50% claim ... but they're both relatively the same for us here on Earth. Day Length Day length is a great thing for solar panels. Domes could keep people from the full effect of the day anyways. It could be regulated in any manner they wish. Something like transition lens windows or something. Theres plenty of other things they'd have to get used to, time of day seems pretty meager. If we are looking at creature comforts like this as a benefit, perhaps it should be mentioned that being able to see the earth at all times out your window would be quite a mole booster and would help people cope with many of the inconveniences of space life. Resources I still believe it would cost more than actually mining the resources there on the planet. I believe this on the grounds that a vertical business model start up would be hugely less cost efficient when you already have all of the processing set up for these materials here on earth. There are also inherent benefits to having processed materials here on earth under its pressures and natural environment. You're talking about also having to develop entirely new methods of processing materials given the gravity, pressure difference, and atmosphere we made mention to earlier. That's a lot lot more engineering cost accrued vs. The tried and true methods we already have in place. Habitability It may be a long way off. But its a long long long way off. Like I said ... barring a celestial level change in the planets location to the sun ... or a change in the sun itself ... creating a permanent atmosphere of oxygen like that of earth on mars is not doable. There is a natural reason for why all of its oxygen escaped its atmosphere before. And like I said, the water all would have followed it too, were it not frozen there. Melting it is just assisting the planets loss of its water. Think of it as having a much much lower threshold for global warming than the earth. Its ability to hold an atmosphere is already very small. Forcing events, like purposely melting polar icecaps, would speed those effects along at a much faster rate on Mars than how we are seeing them here on Earth. Its a much more sensitive environment, since its not naturally prone to holding one on its own. I'm certain we'd destroy any chance in using it in the future if we tried now. We'd need to wait till we could move it or the 'Goldilocks Zone' for the sun expanded a bit and encompassed Mars.