Diamond dust discovered in Canada appears to bolster the theory that an asteroid impact may have wiped out the dinosaurs some 65 million years ago, scientists reported Wednesday.
The microscopic diamonds, found in 65 million-year-old clay stone in Alberta's Red Deer Valley, were present at concentrations indicating they may have originated in a carbon-bearing comet or asteroid, researchers said.A debate over what killed the dinosaurs and many other life forms at the end of the Cretaceous period has raged since 1980, when Nobel Laureate Luis Alvarez and his son Walter proposed the cause was a huge asteroid or comet slamming into Earth.
However, other scientists argue that Earth-bound forces like volcanoes could account for the mass extinction.
Evidence amassed in support of the "killer" asteroid theory include larger than normal quantities of the metal iridium in rocks dating back to the end of the Cretaceous, as well as a worldwide layer of soot and glass fragments typical of those formed when asteroids strike Earth.
Now, a pair of Canadian researchers report their newly discovered diamond dust "strengthens further the case for an extraterrestrial impact."
David Calisle of Environment Canada in Ottawa and Dennis Braman of the Royal Tyrell Museum of Paleontology in Drumheller, Alberta, said they think the diamonds were either contained in an asteroid or possibly formed when an asteroid crashed into carbon-rich rocks.
"The (diamond) powder cannot have originated in volcanic action because the mircodiamonds would have reverted to graphite or oxidized to carbon dioxide at the temperatures and relatively low pressures characteristic of volcanic eruptions," the scientists write in a study published in the British journal Nature.
However, Charles Officer of Dartmouth College in Hanover, N.J., a critic of the asteroid model of extinction, said high-pressure volcanic eruptions that emanate from deep within the Earth are capable of creating diamonds. Rocks that have congealed from a molten mass are also associated with diamond deposits throughout the world, he said.
Furthermore, Officer said diamonds are not a common feature of meteorites. "I'm afraid this (latest work) does not solve the problem," he said.