Martin Schmieder, a geo-chronologist from the University of Western Australia, and his colleagues have debunked the long-held belief that the Clearwater Lakes in Canada was formed by twin asteroids crashing on Earth.

Schmieder's research suggests that one of the two circular pits in Quebec is approximately 200 million years younger than the other. The eastern lake, he said, is around 460 to 470 million years old, which puts it in the Ordovician era, while western lake was formed roughly around 286 million years ago in the Permian era.

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A continuous body of water, the lakes are partially separated by a band of islands less than 10km wide.

An international team led by Schmeider examined core samples that were obtained in the 1960s and 1970s by the Canadian Geological Survey.

"At that time the prevalent theory was that these craters were like a doublet impact crater," he said. "That was something that we wanted to check, especially as there was a 1990 publication that had suggested there was something wrong with those ages."

The team used a dating technique which monitors potassium 40 levels, called the argon-argon dating method, present in the samples.

He said that the team was looking for melt rocks, which are rocks that would have melted if an impact from an asteroid if such an event would occur.

"These rocks usually experience temperatures in excess of 2,000 degrees which also reset that potassium argon clock."

The technique for dating involved bombarding samples of melt rock inside a nuclear reactor with neutrons and then processing the samples in a mass spectrometer.

"Using that mass spectrometer nowadays you can actually obtain ages with fairly good accuracy down to the hundred, or even ten thousand, year levels," Schmieder said.

The findings of the research team suggest that the lakes were formed by two different impacts that just happened to be within proximity with one another.

Eric Tohver, a co-author of the study, said the 50-year-old hypothesis  had a basis that was understandable.

"The idea that a meteorite could hit very close to a previous meteorite has always been dismissed or considered to be so improbable as to be impossible," he said.

TagsClearwater Lakes, Melt rock, Argon-argon dating, Potassium 40, Asteroid impact, Lakes, Canada Clearwater Lakes