If we had a colony on Mars and the Earth was hit by a killer asteroid, everyone on Mars would be dead before long, as well. We are very far from having the technology to survive on Mars indefinitely without a great deal of support from Earth.rstevenson wrote:Establishing off-world colonies to protect ourselves from ourselves would indeed be absurd, if that was the only reason. Protecting our race from the universe is more to the point. We don't want to be watching the approach of the killer asteroid while thinking, "Gee, I guess we should have started a Mars colony years ago. Oh well, too late now!"
Your argument is fine when we're considering the distant future. But I'd laugh at somebody proposing we spend money for a manned Mars mission for the purpose of taking all our eggs out of a single basket.