Terraforming: it's made for some great images in sci-fi movies, and provided comforting fantasies for people worried about the Earth no longer being able to sustain human life: we go to another planet, seed it skillfully with the ingredients of an Earth-like atmosphere, and boom! one instant paradise of a pristine planet full of lush vegatation, untouched by Man.
"Untouched by Man," and yet also 100% human-made. Yes. Well. Moving on --
Neil deGrasse Tyson has a wondeful show on National Geographic TV, "StarTalk," which also is and/or used to be a radio show and podcast, and different episodes feature different co-hosts, and on a recent episode the co-host was the comedian Eugene Mirman, and Mirman is more than just a pretty face, he's also wicked smart.
And someone brought up the subject of terraforming Mars, and Tyson provided the discouraging information that terraforming Mars would be extremely difficult because of factors such as: it hasn't rained on Mars in BILLIONS of years -- and Mirman interjected: "Terraform Earth!" And Tyson beamed and gave Mirman such a proud look, like: "Bingo! This is why you're on my show!"
We can make this planet inhabitable, much more easily than we can any other planet. Put it on bumperstickers, T-shirts and billboards: