Read Isaac Asimov's Utopia Storyline:
The world of Inferno is dying. A world where Spacers work with Settlers, where standard Three-Law robots exist alongside the controversial New-Law robots. A world that will be uninhabitable in a few decades. Their only hope comes from a plan some call insane, and some call visionary: drop a comet on the planet.Pages of Isaac Asimov's Utopia :