The shimmering red presence

I saw a bumper sticker that neatly summarized the impulse to action on climate change: There is no planet B

Recently, though there's been a flicker of interest, spurred by the confluence of the discovery of liquid water on Mars, a fictional tale of a marooned astronaut, and the presence of Elon Musk, in the idea that we might someday flee to Mars, leaving behind the hoarder hellhole we've made of the Earth. 

How hard could it be to terraform Mars, if we really bent our will/money to the task? Before you answer, consider that the survival of our species (or at least, the survival of a technological society) might be at stake. Does that open up your wallets, humanity?

Wait, before you answer, consider this: Why Don't We Just Terraform Earth?