Experts Estimate Asteroid Risk

At a NASA-sponsored conference, a group of experts have estimated that the Earth is struck once every 1,000 years by an asteroid capable of releasing 10-megatons of energy - not a planet killer, but definitely enough to cause a terrible loss of life. NASA and the astronomical community has been systematically searching for all Near Earth Objects larger than 1 km across, and capable of crossing the Earth's orbit. So far they've found 600 out of an estimated 1,000.