Isaac Asimov's "Utopia"

In a universe protected by the Three Laws of Robotics, humans are safe. The Third Law states, A robot must protect its own existence as long as such protection does not conflict with the First or Second Law. 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. The impact could create new rivers that would save the planet but it could also destroy Inferno completely! Now the Spacers of Inferno must take a risk. A risk that their robots, pledged to protect humans from any harm, real or imagined, may not let them take...