> People often say, if you think you can colonize mars, colonize the Gobi Desert first, as it is 10,000 times easier.

If we're talking about population living on earth, that argument makes sense - from a population pressure standpoint , there's no argument to go to mars.

But if we're talking about civilization expanding from more resources, with some space where you can potentially crash land a few asteroids while trying to pull it into orbit for easier mining, then Earth is out of question.