Last Christmas, an asteroid soared from obscurity to become the riskiest space rock ever detected. But soon its odds of Earth impact plummeted … and then rose again. What gives with all the meteoric melodrama?

How do you find an asteroid in a celestial crowd? First, bring a camera. Second, shoot anything that moves.

Meteorite specialist Dr. Denton Ebel talks asteroids bigger than Everest, glass mini-marbles raining from the sky, and dinosaur toast.