For more information about terraforming check out "Terraforming Mars - Astrobiology Perspectives on Life in the Universe" by Martin Beech and "The Future of Humanity" by Michio Kaku.

“The key question for terraforming is the amount of CO 2, N 2, and H 2 O on Mars. Unfortunately there is nothing new here to resolve this question,” McKay emails.

Now, scientists are saying it’s time to treat it as science. “Thirty years ago, terraforming Mars wasn’t just hard — it was impossible,” DeBenedictis told Space.com.

Of course, under no circumstances should we consider abandoning Earth for Mars; any terraforming we'd do to the red planet would be far more intensive than anything we'd need to do to save the Earth.

If future Mars colonizers want to survive without pressure suits, they’ll need to generate a denser atmosphere. One way to achieve this could be to bombard the Red Planet with water-rich asteroids.