Doesn't solve the fact that there just isn't enough material to heat (ice and rock) to create enough of an atmosphere for decent pressure without importing mass

Doesn't solve the fact that there just isn't enough material to heat (ice and rock) to create enough of an atmosphere for decent pressure without importing massive amounts via asteroids. I'm all for manned exploration of Mars, I think the amount of science a team of humans can do during the necessary mission times (while waiting for the launch window for the quickest return) will be insane. Actually, the amount of science humans could do in a WEEK would likely generate more data, and more discoveries, than every probe and rover sent to Mars to date. I think the extreme risks to the crew, which may remove any reasonable hope for a good qualify of life upon return, and could result in fatal cancer, is absolutely worth the sacrifice as long as the crew is 100% volunteers that have adequately been explained the myriad of risks. That said, as cool as it would be to colonize another planet, Mars just isn't going to realistically be it. Not until we are well on our way to being a Type II civilization (arguably we are still decades, at least, from being a Type I) but constructing something like O'Neill cylinders is far more realistic, as long as we can figure out asteroid mining (especially if we can automate it).