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Agence France-Presse

Around 66 million years ago, an asteroid bigger than Mount Everest smashed into Earth, killing off three quarters of all life on the planet – including the dinosaurs.
This much we know.
But exactly how the impact of the asteroid Chicxulub caused all those animals to go extinct has remained a matter of debate.
The leading theory recently has been that sulphur from the asteroid’s impact – or soot from global wildfires it sparked – blocked out the sky and plunged the world into a long, dark winter, killing all but the lucky few.
However research published Monday based on particles found at a key fossil site reasserted an earlier hypothesis: that the impact winter was caused by dust kicked up by the asteroid.
Fine silicate dust from pulverised rock would have stayed in the atmosphere for 15 years, dropping global temperatures by up to 15 degrees Celsius, researchers said in a study in the journal Nature Geoscience.
Back in 1980, father-and-son scientists Luis and Walter Alvarez first proposed that the dinosaurs were killed off by an asteroid strike that shrouded the world in dust.
Their claim was initially met with some scepticism – until a decade later when the massive crater of Chicxulub was found in what is now the Yucatan Peninsula on the Gulf of Mexico.

Now, scientists largely agree that Chicxulub was to blame.
But the idea that it was sulphur, rather than dust, that caused the impact winter has become “very popular” in recent years, Ozgur Karatekin, a researcher at the Royal Observatory of Belgium, said.
Study co-author Karatekin said this was because the dust from the impact was thought to be the wrong size to stay in the atmosphere for long enough.
For the study, the international team of researchers was able to measure dust particles thought to be from right after the asteroid struck
‘Planet killer’ asteroids detected after being hidden by sun’s brightness
The particles were found at the Tanis fossil site in the US state of North Dakota.
Though 3,000km (1,865 miles) away from the crater, the site has preserved a number of remarkable finds believed to be dated from directly after the asteroid impact in sediment layers of an ancient lake.
The dust particles were around 0.8 to 8.0 micrometers – just the right size to stick around in the atmosphere for up to 15 years, the researchers said.
Entering this data into climate models similar to those used for current-day Earth, the researchers determined that dust likely played a far greater role in the mass extinction than had previously been thought.
Out of all the material that was shot into the atmosphere by the asteroid, they estimated that it was 75 per cent dust, 24 per cent sulphur and one per cent soot.
The dust particles “totally shut down photosynthesis” in plants for at least a year, causing a “catastrophic collapse” of life, Karatekin said.
Sean Gulick, a geophysicist at the University of Texas at Austin and not involved in the research, said that the study was another interesting effort to answer the “hot question” – what drove the impact winter – but did not provide the definitive answer.
He emphasised that discovering what happened during the world’s last mass extinction event was important not just for understanding the past, but also the future.
“Maybe we can better predict our own mass extinction that we’re probably in the middle of,” Gulick said.
Additional reporting by Reuters


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Science

Asteroid dust caused 15-year winter that killed dinosaurs, study says

This artist’s reconstruction depicts North Dakota in the first months following the impact of an asteroid off Mexico’s coast 66 million years ago. Photo: Mark A. Garlick via Reuters

Sediment at a North Dakota paleontological site called Tanis has preserved evidence of the post-impact conditions. Photo: Pim Kaskes via Reuters

Chinese-led team reports first evidence of puberty in dinosaur-era reptile, offering new insight into sexual development

An artist’s rendering of the underwater dinosaur Keichousaurus. Researchers from China, Japan and Germany report that Keichousaurus males developed features distinct from females and reached sexual maturation through a process of puberty. Image: @Takumi

Humerus and thin sections of two sexes of Keichousaurus. Image: Hefei University of Technology

T. rex had lips to hide those giant teeth, scientists say

An illustration depicts a juvenile Edmontosaurus being eaten by a Tyrannosaurus rex with a lipped mouth. Image: Mark P. Witton via AP

An illustration shows two principal models of predatory dinosaur facial appearance: crocodilian-like lipless jaws (above) or a lizardlike lipped mouth. Image: Mark P. Witton via AP

The skeleton of “Sue” the Tyrannosaurus rex is displayed at the Field Museum of Natural History in Chicago. Photo: Field Museum via Reuters 

China’s rock samples brought back from the moon shed light on meteor strikes here on Earth, say scientists

The Chang’e 5 probe returned to Earth in December 2020 with 1.7kg (3.74lbs) of rocks and dust from Oceanus Procellarum on the moon. Photo: Handout

Ancient eggshells show dinosaurs already dying out before asteroid strike, Chinese scientists say

An artist’s depiction shows Chinese scientists’ view of late Cretaceous oviraptorosaurs, hadrosaurs, and tyrannosaurs living in central China. Image: Chuang Zhao.

A dinosaur egg (Macroolithus yaotunensis). Photo: Wang Qiang  (Institute of Vertebrate Paleontology and Paleoanthropology, Beijing, China), Han Fei and Wen Chen (China University of Geosciences, Wuhan, China)

News

World

Asteroid smacked Mexico’s Yucatan Peninsula 66 million years ago, causing a global calamity
Research suggests dust from pulverised rock at the impact site fouled Earth’s atmosphere


It was, to put it mildly, a bad day on Earth when an asteroid smacked Mexico’s Yucatan Peninsula 66 million years ago.


Asteroid dust caused 15-year winter that killed dinosaurs, study says

.css-1mniedq{color:inherit;font-weight:inherit;font-size:inherit;font-family:inherit;line-height:inherit;}Asteroid smacked Mexico’s Yucatan Peninsula 66 million years ago, causing a global calamity Research suggests dust from pulverised rock at the impact site fouled Earth’s atmosphere

Asteroid smacked Mexico’s Yucatan Peninsula 66 million years ago, causing a global calamity

Research suggests dust from pulverised rock at the impact site fouled Earth’s atmosphere