A huge meteor, 15 kilometers across, came whizzing out of space and slammed into the earth's surface 66 million years ago, scientists say.
The impact threw so much dust and dirt into the atmosphere that the world was plunged into an extended "global winter." At least 75 percent of all living species went extinct in the aftermath of the impact, the greatest extinction event in the history of the planet.
Researchers who have studied the huge impact crater left behind in the Caribbean say the asteroid hit the planet in the worst possible place. The impact site was covered by a shallow sea in those days, resting upon soil that was saturated with the mineral gypsum. The asteroid's impact released a huge volume of sulphur into the atmosphere, which made the "global winter" more severe and long-lasting.
If the asteroid had hit the planet almost anywhere else, many more species would likely have survived.
"This is where we get to the great irony of the story – because in the end it wasn’t the size of the asteroid, the scale of blast, or even its global reach that made dinosaurs extinct – it was where the impact happened," said Ben Garrod, who studied the blast with scientists in preparation for hosting the documentary "The Day the Dinosaurs Died."
"An impact in the nearby Atlantic or Pacific oceans would have meant much less vaporized rock – including the deadly gypsum," he said. "The cloud would have been less dense and sunlight could still have reached the planet’s surface, meaning what happened next might have been avoided. In this cold, dark world food ran out of the oceans within a week and shortly after on land. With nothing to eat anywhere on the planet, the mighty dinosaurs stood little chance of survival."