It has long been believed dinosaurs had been wiped out after an asteroid struck Earth off the coast of Mexico. Now scientists have dug through half a mile of rock at the impact site to examine the remains of the asteroid. They determined it was nine miles wide and hit the Earth at a speed of 40,000 miles per hour. The asteroid strike made a hole that was 20 miles deep and 120 miles wide. But the size of the asteroid cannot account for wiping out the dinosaurs. The relative size of the asteroid and the Earth was like a grain of sand striking a bowling ball.
Scientists discovered the impact site, named Chicxulub, in 1991 but did not know why such a minor impact caused such devastating changes to the Earth. Until now. The scientists learned the rocks at the impact area are rich in sulphates and the impact caused more than 100 billion tons of sulphur to be spewed into the atmosphere. According to Sean Gulick, a professor of geophysics at the University of Texas, Austin, sulphur particles reflect light and blocked out the Sun. This caused the Earth to dramatically cool for about a decade. Plant life died, leading to a shortage of food.
Joanna Morgan, of Imperial College London, one of the researchers, said, “That would be enough to cool the planet for a decade and wipe out most life.” Dinosaurs not directly killed by the impact would have frozen to death or starved. But small mammals were not only able to survive but they thrived and evolved after the destruction of larger predators.
Professor Alice Roberts, said half a million years after dinosaurs became extinct, Earth was filled with different kinds of mammals. According to the professor, were it not for the asteroid strike, we would probably not be here.
But had the asteroid struck Earth 30 seconds earlier or 30 seconds later, the results would have been vastly different. The asteroid would have landed in either the Pacific or Atlantic oceans and while a lot of water would have been vaporized, the amount of vaporized rock would have been much less. Another 30 seconds either way and dinosaurs might still roam the Earth.
A documentary on the research will be aired tonight by BBC2. Entitled The Day the Dinosaurs Died, it will be hosted by Professors Alice Roberts and Ben Garod.
