This appeared last week:
Asteroid dust caused winter that killed dinosaurs: study
By Daniel Lawler
AFP
Updated 5:24PM October 31, 2023, First published at 2:12PM October 31, 2023
About 66 million years ago, an asteroid bigger than Mt 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 become extinct has remained a matter of debate.
The leading theory recently has been that sulphur from the asteroid’s impact – or soot from global bushfires it sparked – blocked out the sky and plunged the world into a long, dark winter, killing all but the lucky few.
But new research based on particles found at a key fossil site reasserted an earlier hypothesis: that the 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 up to 15C, researchers report in the journal Nature Geoscience.
Father-and-son scientists Luis and Walter Alvarez in 1980 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 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.
Dr Karatekin, a co-author of the study, said the international team of researchers was able to measure dust particles thought to be from right after the asteroid struck. The particles were found at the Tanis fossil site in North Dakota. Though 3000km away from the crater, the site has preserved several remarkable finds believed to be dated from directly after the asteroid impact in sediment layers of an ancient lake.
The dust particles were between 0.8 to 8.0 micrometres – just the right size to stick around in the atmosphere for up to 15 years.
Out of all the material that was shot into the atmosphere by the asteroid, the researchers estimated that it was 75 per cent dust, 24 per cent sulphur and 1 per cent soot.
More here:
I do feel rather sorry for all our old mates but something had to give our ancestors a chance to dominate. I wonder what will eventually come along to wipe us off and give another species a chance?
David.
No comments:
Post a Comment