The frontier in space, embodied in the space colony, is one in which the interactions between humans and their environment is so much more sensitive and interactive and less tolerant of irresponsibility than it is on the whole surface of the Earth.

It would take an extremely large spacecraft to deflect a large asteroid that would be headed directly for the Earth.

We have the capability - physically, technically - to protect the Earth from asteroid impacts. We are now able to very slightly and subtly reshape the solar system in order to enhance human survival.