Dinosaurs were roasted to death by asteroid dust cloud
Researchers say ejected dust acted like lid on a pot, trapping heat and ‘charbroiling’ anything that could not reach safety
Dinosaurs roasted to death in a hellish “oven” created by superheated dust when an asteroid hit Earth 66m years ago, scientists believe.
When the Everest-sized space rock hit the planet at 45,000mph, it vaporised anything in its path and ignited landscapes within a 900-mile radius.
But planetary scientists at Purdue University, in the United States, believe some dinosaurs may have survived had it not been for a suffocating cloud of ejected dust, which sat like a lid over Earth and prevented the blast heat from escaping into space.
Dr Alexandria Johnson, an expert in atmospheric sciences, said: “Anything that couldn’t shelter itself somehow – underground or underwater – would have got baked or fried.”
The Chicxulub asteroid sent more than 240 cubic miles of material into the atmosphere, some of which condensed into droplets of rock – spherules – which fell back to Earth, heating the air further.
Prof Brandon Johnson, of the department of Earth, atmospheric and planetary sciences at Purdue, said: “With the dust cloud trapping thermal radiation, it was like the surface and everything on it was being charbroiled – and that’s what killed the dinosaurs and all the other animals.
“It’s not the blast wave from the impact or the fireball – those don’t go very far. It’s the global ejection of this vapour plume material that makes this a global extinction event.
“Without the dust cloud, it would have been bad. It would have killed a lot of creatures, but it wouldn’t have been a planetary catastrophe.”
The Chicxulub impact near the Yucatán Peninsula is believed to have killed about three-quarters of all living species, including most of the dinosaurs. Only the avian dinosaurs survived.
Previously, experts believed the asteroid triggered giant tsunamis and created a cloud that blocked the sun for years, causing plummeting temperatures and killing plants that starved dinosaurs that ate vegetation. When the plant-eaters died, the meat-eaters also died.
But the new study suggests that, for most animals, the apocalypse probably occurred much more quickly.
Researchers calculated that the heat trapped by the fine dust meant the dinosaurs received a dose of thermal radiation 17 times more than the amount that would be lethal to humans.
The intense heat was enough to ignite grass, pine needles, lichen and maybe even wood, causing widespread wildfires and turning Earth into a fiery oven from which only burrowing animals, and those in the sea, could escape.
“It probably looked more like hell,” said Prof Johnson. “The clouds would have blocked daylight so to any animal, like humans, that don’t see far into the infrared, the surface would have probably looked dark.”
Scientists knew that the impact had melted rocks and sent detritus showering down to Earth because spherules have been found in the gills of paddlefish, which probably died on the day the asteroid hit.
The spherules, about half the size of a grain of sugar, were made up of material of terrestrial origin – not from the asteroid itself, but almost certainly the deadly cloud that it created.
Dr Johnson looked at the physical properties of these particles and the dust cloud as a whole to determine how it would have handled heat.
She found the cloud layer was so impermeable that it trapped almost all of the heat from near the surface of the planet, the dust essentially acting like a lid on a pot, cooking Earth’s inhabitants on the surface.
The dust could have taken years, or even decades, to settle, and the particles themselves could have caused ongoing health problems for survivors.
The study was published in the Journal of Geophysical Research: Biogeosciences.
