The asteroid that exploded over Siberia—injuring more than 1,000 and damaging buildings in six cities—was a shocking reminder that Earth is a target in a cosmic shooting range. From the width of a football field to the size of a small city, these space rocks have the potential to be killers. In a collision with Earth, they could set off deadly blast waves, raging fires and colossal tidal waves.

Watch the NOVA video:

But some audacious entrepreneurs look up at asteroids and see payday, not doomsday. NASA is planning an ambitious mission to return samples from a potentially hazardous asteroid.

Will asteroids turn out to be our economic salvation—or instruments of extinction?