A 16-strong team of international boffins have added more evidence for the controversial theory that a gigantic asteroid smashed into the Earth 12,900 years ago and wiped out a range of furry mammals, including the mammoths.
The researchers found an ancient layer of thin, dark sediment buried at the bottom of Lake Cuitzeo in central Mexico that contains nano diamonds, impact spherules and other exotic materials that are only found after a cosmic impact.
The study shows that an asteroid that was probably bigger than several hundred metres in diameter and blasted through the atmosphere at a shallow angle, burning up biomass, melting surface rocks and causing major environmental disruption.
"These results are consistent with earlier reported discoveries throughout North America of abrupt ecosystem change, megafaunal extinction, and human cultural change and population reduction," James Kennett, professor of earth science at UC Santa Barbara, said in a tinned statement.
The sediment layer under Lake Cuitzeo is the same age as layers previously found in numerous locations in North America, Greenland and Western Europe, extending the asteroid's range into Mexico and the tropics for the first time.
This species-destroying asteroid is one of only two that boffins have found evidence for in sediment layers, the other being the dino-destroying rock that hurtled into the planet 65 million years ago. The second impact took place 12,900 years ago at the onset of an unusual cold climatic period called the Younger Dryas.
"The timing of the impact event coincided with the most extraordinary biotic and environmental changes over Mexico and Central America during the last approximately 20,000 years, as recorded by others in several regional lake deposits," said Kennett.
"These changes were large, abrupt, and unprecedented, and had been recorded and identified by earlier investigators as a ‘time of crisis.' "
The mammoth-murdering asteroid is also associated with the extinction of other North American animals including mastodons, sabre-tooth cats and dire wolves.
The study was published in the Proceedings of the National Academy of Sciences. ®