Asteroid strike caused global firestorm that incinerated the dinosaurs
· New Scientist
The asteroid strike 66 million years ago caused a planetary-scale firestorm that burned dinosaurs to a crisp all over the world, according to simulations of the impact.
The so-called Chicxulub asteroid, which was 10 to 15 kilometres wide, landed in what is today the Gulf of Mexico at the end of the Cretaceous Period.
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Until now, it has been thought that most of the worst effects of heat and fires would have been relatively regional, and global extinctions were mainly caused by a “nuclear winter”, where dust blocks out the sun causes dramatic cooling.
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if( window?.adverts?.addToArray ) { window.adverts.addToArray( { "pos": "mid-article-slot" } ); }Brandon Johnson at Purdue University, Indiana, and his colleagues analysed geological observations and impact simulations in the laboratory, which showed around five times more material was vaporised by the strike than previously thought.
The new work suggests that in the aftermath of the impact, a plume of rock vapour was blasted tens of thousands of kilometres into space and ended up being distributed high above the entirety of the planet.
Sign up to The Earth Edition Sign up to newsletter“After the impactor first strikes the Earth, it only takes about a second for much of the kinetic energy to be converted to heat, vaporising over 1000 cubic kilometres of rock,” says Johnson.
Just seconds later, the vapour plume expanded above much of Earth’s atmosphere into space, he says, leading to both dust and glassy, metallic beads called spherules, condensing from the vapour.
This immense vapour cloud ultimately turned into 1.6 trillion tonnes of dust, which blanketed the planet, sealing in heat, the study found. Meanwhile, the heavier spherules slammed back into the atmosphere.
“As this material re-enters the atmosphere over the coming hours, friction decelerates and heats the spherules, creating an approximately hour-long pulse of thermal radiation,” says Johnson.
“This would kill off creatures that were unable to shelter from it and was intense enough to ignite forest litter like grass and pine needles and may have even been enough to ignite trees.”
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The geologic record suggests the ensuing fires may have lasted for years and would have been reminiscent of the bushfires currently gripping Europe, except on a global scale, he says.
“The Cretaceous animals would have received 17 times the dose of thermal radiation that is 100 per cent lethal to humans,” says Johnson. “That should be enough to kill off even thick-skinned dinosaurs.”
Craig O’Neill at the Queensland University of Technology in Australia says the study shows that the dust layer encircling the planet was essentially opaque to infrared and visible light, trapping the heat.
“Every joule of heat created by incoming spherules is turned into a thermal pulse that bakes the surface of the Earth,” says O’Neill. “For about 30 minutes, the land is turned into history’s largest barbecue.”
However, this isn’t the whole story, he says. For example, life in the oceans was also badly affected by the event, driving many marine animals such as mosasaurs and ammonites extinct. This is better explained by the effects of a nuclear winter blocking out the sun on photosynthesising organisms, rather than an atmospheric thermal pulse, says O’Neill.
“We tend to think of mass extinction events as a murder mystery – if we can just find the murder weapon, we could solve the case. But mass extinctions seem more like a cascading system of failures,” he says.
Journal Reference:Journal of Geophysical Research Biogeosciences DOI: 10.1029/2026JG009837