NASA's latest Mars rover, Curiosity, is currently its way to Mars, on a mission to explore whether life could exist there. If we're going to colonize Mars — and some scientists say we must — it's likely that we'll start by terraforming. Terraforming, or planetary engineering, is the process of altering the climate of a planet to be more hospitable to life and human exploration. Of all the bodies in the solar system, Mars is by far the best candidate. Here's how that would work.