This theory has been around for a while. I think David Brin and Gregory Benford mentioned it in their coauthored novel "Heart of the Comet." It may have been mentioned in some the numerous other Mars habitation books out there. I haven\'t read any of them though. Obviously we lack the technology to alter a comet\'s course at the moment, and I don\'t think even 59 years will give us enough time to do it. Maybe on Halley\'s next orbit after that we might be ready.
I believe another idea was to detonate nuclear weapons on Mars, thus putting a great deal of dust into the atmosphere, triggering a greenhouse effect, raising the surface temperature, and therefore melting some of the frozen water at the poles. I think there was some theoretical snag in that plan too, but I don\'t remember what it was.
However it\'s done, I\'m sure we will be living on Mars eventually. It\'s inevitable, because some day we won\'t have enough space on Earth. I wouldn\'t count on it happening any sooner than about 150 years from now.