This seems like a response tediously intent on missing the point: if you genuinely want to build a sustainable settlement on Mars, you should start by proving out sustainable settlements in harsh environments on Earth -- you could build out sustainable settlements in the Antarctic, the depths of the Sahara, and under the ocean all with substantially less expense/risk than trying to build a sustainable settlement on Mars. You'd learn how to build better sustainable settlements by doing so and encounter some of the problems you'll encounter on Mars with less dire consequences. And you don't have to choose one or the other: you can parallel path it by continuing to improve rocketry while building up sustainability strategies in harsh environments on Earth. The fact that Musk is intent on reaching Mars as the only difficult problem just underscores that he is not serious about settling Mars (or, perhaps, that he simply isn't that bright).