New doubt cast on dinosaur-killing asteroid theory

The asteroid blamed for a mass extinction event 65 million years ago could actually predate the demise of dinosaurs by 300,000 years.

By analysing sediments near the asteroid's site of impact, called the Chicxulub crater, researchers have found that the impact did not cause the extinction of any species.

In the Mexican town of El Penon, Princeton University geologist Gerta Keller and her research team found evidence of 52 species in sediments that were deposited both before, and after, the impact.

"We found that not a single species went extinct as a result of the Chicxulub impact," she said.

Keller's report contradicts the popular theory that the Chicxulub impact heralded the extinction of 65 percent of all species, including plants, dinosaurs, and other animals.

She expects her findings to be unsurprising, as no other great mass extinctions are associated with an impact, and no other large craters are known to have caused a significant extinction event.

Keller suggests that the massive volcanic eruptions at the Deccan Traps in India may be responsible for the extinction.

Huge amounts of dust and gases from the eruptions could have blocked out sunlight and brought about a significant greenhouse effect, she said.

More information is available from the National Science Foundation's press release.