Zooming in from space, asteroids have struck the earth in the past and will do so again in the future. How astronomers search near space for these "flying rocks" and devise ways to avoid an impact that, in a worst-case scenario, could eliminate civilization.

Home of the asteroids -- Four stories, three true -- Target earth -- Playground of the asteroids -- The missing planet -- Birth of the asteroids -- Dead comets -- Asteroids bombing earth -- Stones from heaven -- Disappearing dinosaurs -- Loose cannonballs -- The incoming asteroid -- Asteroid hunters -- Outposts in space -- Your own space rock.