True, but I believe there are difficulties such as the lack of a magneticsphere on the planet, and the minimal (if any) atmosphere. Lighter elements simply float away from planet. There are so many ideas regarding terraforming and bringing Mars back to life, but with the core of the planetbeing dead, and this being an issue that the pro-terraformers don't address, I have troubling believing that it can be done.
Now, if we were to get Arnold and that dude with the little dude growing on his chest up there, we'd have water, air, atmosphere on Mars in...5 minutes.
GO TO MARS! Recall!