Living Off Earth
Humans, as we currently exist require oxygen under pressure, water, food, decent gravity, low-radiation levels, and temperatures in a quite narrow range from our environment. None of these exist on Mars or the Moon or in open space. So, if we are to survive off Earth, then first we need to solve these. Once they are all solved, then Mars is no better than say the Asteroid Belt with the possible exception of it's 3.711m/s² gravity field.
If we want to survive away from our home planet then Mars is just another resource, but the Asteroid belt has those resources in a nice cheap low-g environment where they are comparatively easy to get at and exploit. Mars is irrelevant. If we are to survive off Earth then the first step is bigger orbital environments where we can tackle most of these challenges near to home. Grab a decent sized mostly solid asteroid, carefully put it in orbit around Earth, then mine it for resources whilst learning how to live there.
We could also modify ourselves to be able to survive in space, or more likely create our successor species (AI/AS anyone?) such that they can survive anywhere.
I'm with Agent Smith w.r.t. how to label Homo Sapiens' effect on it's environment. Virus is a much better description than Locust.
Biting the hand that feeds IT
