Earlier quoted context omitted.
Deflecting an asteroid with current technology would involve launching a rocket at it and either imparting enough kinetic energy to nudge it into an orbit that doesn't intersect Earth or blowing it up with a nuclear warhead. Either of those would require a large rocket capable of throwing a substantial payload well outside of Earth's orbit. Tracking asteroids can be done with terrestrial radar (that was one of the th…
The problem is that there is no economic case for ferrying stuff to and from Mars. There is nearly nothing on Mars that anyone on Earth will pay a premium that will pay the costs of colonization off. It's the ultimate exercise of ditch-digging, and ditch-filling, with the justification that doing so accelerates the technological development of ditch-digging instruments. Which is both technically correct, and also com…
Any potential Mars colony is likely to be populated by an early group of scientists and tourists, but there are a lot of other reasons people might want to visit Mars or stay there. Mining of high-value minerals. Filming TV shows and movies. Sports. Claiming the best real estate before someone else does. Establishing a refueling station between Earth and the asteroid belt. Manufacturing heavy space equipment that we don't want to lift out of Earth's gravity well. Some people with mobility issues might rather live in low gravity on Mars than be bound to a wheelchair on Earth. And so on.