Stock Photo - Artwork depicting the extinction of the dinosaurs, some 65 million years ago ... . Scientists are now as certain as they can be that the extinction of the dinosaurs was at least partly provoked by the impact of a giant asteroid or comet in a shallow sea off the coast of what is now Mexico. The bolide is thought to have been around 10 kilometres (6 miles) across. Debris from the impact would have been thrown high into the atmosphere, blocking the Sun's rays for months, maybe years - killing all plant life, the animals that fed on them, and their predators. The dinosaur parasaurolophus, and the flying reptile pteranodon, both depicted in this image, were among those animals wiped out by this catastrophic event.