Scientists say atomic dating of droplets of melted glass found in Haiti lends new support for a theory that an asteroid collision with the Earth 64 million years ago killed off the dinosaurs.
A report in the journal Science said U.S. Geological Survey scientists have proven that tektites - small bits of glass formed when a boulder from outer space smashed into the Earth - were created at the same time as the mass extinction of the dinosaurs.USGS researcher Glen A. Izett said the tektites were found in Haitian formations with two other materials also thought to have originated from asteroid or comet impacts.
The other materials are iridium, an element rare on Earth but common in asteroids, and shocked quartz grains, bits of rock that bear scars of a violent impact. By dating the tektites, the iridium and shocked quartz are also dated.
"We dated 23 of these little critters and they turn out to be 64 to 65 million years old," Izett said. Fossil records have established that this was the period in which the dinosaurs died out.
Eugene Shoemaker of the USGS office in Tucson, Ariz., a prominent expert on asteroid and comet collisions with Earth, said the tektite dating study is "a very important indication of a large impact. This is a valuable addition to our knowledge supporting the theory."
A theory first proposed by Luis W. Alvarez of the University of California suggests that a very large asteroid struck the Earth millions of years ago and filled the sky with dust, smoke and steam. This caused a global climate change that wiped out the dinosaurs, the theory holds.
The Alvarez theory is based on the fact that there is a worldwide geologic layer of iridium deposited at about the same time that fossil records show extinction of dinosaurs and many other animal species.
Now, said Izett, his work puts a precise date on tektites, another proof of a massive impact of an object from space.