Research suggests that the asteroid impact was catastrophic for the dinosaurs, but the strike season may have increased the extinction rate of other species.
Scientists have found evidence that the cataclysmic impact 66 million years ago, which wiped out three-quarters of Earth’s species and created the Chicxulub crater in modern Mexico, occurred in the northern hemisphere’s spring.
The timing means that many animals north of the equator are particularly vulnerable to the intense heat waves released by the collision, which have just emerged from the harsh winter months. The other animals in the south may be better off as it’s fall, especially if they are wandering in burrows.
The direct hit from the asteroid caused a severe global heat wave that proved fatal to many exposed animals. As a result, temperatures are thought to have dropped so badly in nuclear winter that many species were driven to extinction.
“To be able to fight that nuclear winter, you first have to survive the actual impact,” said Melanie While, a paleontologist at Uppsala University in Sweden. “Anything in the Southern Hemisphere already harbored has a better chance of survival.”
When the asteroid collided, it blasted molten rock into space, which crystallized and rained down on Earth as “collision pellets” that same day. Scientists have found some of these pellets lodged in the gills of fossilized paddlefish and sturgeon unearthed from a fossil site called Tanis in North Dakota.
The discovery of more spheres around the fossils suggests that the glass particles were still flocculated when the fish died, linking the time of death to the day, and possibly even hours, of the collision. The fish appear to have died when they were buried alive due to the sediment shaken by the impact.
Writing in nature magazineIn this article, the scientists describe how they determined seasonal cycles in fish bone growth rates, along with changes in carbon isotopes associated with seasonal changes in the abundance of zooplankton, the fish’s staple diet. All results point to fish deaths – and thus asteroid impacts – in the spring. separate search Regarding the fossil published by Professor Philip Manning at the University of Manchester in December, he came to the same conclusion.
It’s unclear whether the small animals in the northern hemisphere are actually worse off than those in the south. There is evidence for this, says Denis Voyten, co-author of the latest study at Uppsala University Northern hemisphere turtles They were wiped out in an asteroid strike, after which the turtles from the south repopulated their habitat.
Dr Daniel Field, assistant professor of vertebrate paleontology at the University of Cambridge, who was not involved in the research, said it was “plausible” that the catastrophe would affect fauna in the Northern Hemisphere more.
“If the asteroid hits a biological hotspot this year for many organisms in the Northern Hemisphere, it may contribute to an extinction rate that will be higher than expected,” he said.
But he added that nothing bigger than a domestic cat survived the asteroid impact and many species could collapse every time they hit. “It is possible that large non-avian dinosaurs would have gone extinct no matter what time the asteroid hit,” he said.
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