For centuries, people have felt that Mars is the world most like our own. Now some people look to a distant future when it will be almost exactly like Earth thanks to a concept called "terraformation," bringing the entire planet to life by creating a warmer, wetter climate on it.
Terraforming would require creating a greenhouse effect around Mars -- pumping its atmosphere full of the same gases that, ironically, are polluting our own planet's atmosphere right now.
Theoretically, this process would raise Mars's temperature enough to turn its ice into water and to thicken its atmosphere. Though such changes could take 100,000 years, the planet might support insect, plant, and microbial life within a few decades.
The terraformation of Mars raises many questions, both technical and ethical. If it were successful, then we would have engineered our way into becoming a multi-planetary race. But in the process, most other Earthly forms of life would also be transplanted. Maybe, then, the human hand in such an expansion wouldn't be entirely our own initiative. Maybe, in some way, it would be part of the natural scheme of things, of life's unstoppable drive to find new niches and its amazing resourcefulness in claiming them.
