An asteroid can literally destroy 80 or 90 percent of the species that are alive on Earth. These are big events. I mean, this is called extinction.

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.

When you look at the origins and evolution of life on Earth, it's been severely affected by asteroid impacts through history.

Rusty Schweickart Quotes