Springing to extinction
BY 花消英气 from 21st Century
Published 2022-03-25
Research suggests the asteroid that made the dinosaurs extinct hit in spring. TUCHONG

Imagine a warm spring day 66 million years ago. Fish would have been swimming in the rivers in an area that’s now North Dakota in the US. Seconds later, the serenity was ended by destruction.

These could have been the very last moments of the dinosaur era when a city-sized asteroid struck Earth, killing off three quarters of all species on the planet. According to a study published in Nature on Feb 23, the asteroid hit in springtime.

Scientists have long been confused over the time of year the asteroid hit, and how some animals managed to survive while dinosaurs didn’t, according to USA Today.

Researchers in 2019 discovered fossilized fishes in North Dakota that died shortly after the asteroid hit Earth. They examined the fossils with a particle accelerator and found out there was seasonal growth on the bones. All fish bone cell densities and volumes can indicate the season. Because the accelerator also could capture the sizes, researchers were able to determine when in the year the asteroid hit, Dennis Voeten, a researcher at Uppsala University in Sweden told USA Today.

The timing of the collision, at least for the Northern Hemisphere, came at a particularly sensitive stage. “I think spring puts a large group of the late Cretaceous biota in a very vulnerable spot because they were out and about looking for food, tending to offspring and trying to build up resources after the harsh winter,” Melanie During, the main author of the study, said at a news briefing.

In the Southern Hemisphere, it was autumn, a season when many creatures prepare for winter. Therefore, life in the Southern Hemisphere was a lot more prepared for this event.

It is unclear whether small animals in the Northern Hemisphere actually did worse than those in the south. There is evidence that Northern Hemisphere turtles were wiped out in the asteroid strike, after which their habitats were later repopulated by turtles from the south, Voeten told The Guardian.

Nothing much larger than a house cat survived the asteroid impact and many species would have been doomed whenever it hit, Daniel Field, an assistant professor at the University of Cambridge in the UK, told The Guardian.

(Translator & Editor: Li Xinzhu AND Luo Sitian)
Serenity  宁静
Asteroid  小行星
Fossilized  石化的
Particle accelerator  粒子加速器
Capture  捕捉
Collision  碰撞
Cretaceous biota  白垩纪生物
Doomed  劫数难逃的