Asteroid attack 1 - an answer? - What Really Killed the Dinosaurs? - BBC

For 140 million years, the supremacy of the dinosaur on planet Earth was unchallenged. BBC Horizon's 'What really killed the dinosaurs' explores the potential explanation for the disappearance of the most fierce animals ever to walk the Earth. Visit http://www.bbcearth.com for all the latest animal news and wildlife videos and watch more high quality videos on the new BBC Earth YouTube channel