25-kilometre-wide meteorite crater discovered in Arctic
Published Wednesday, July 25, 2012 1:50PM EDT
Last Updated Saturday, July 28, 2012 12:56PM EDT
SASKATOON -- Canadian researchers say they've discovered a 25-kilometre-wide meteorite crater in the western Arctic while they were updating maps.
University of Saskatchewan professor Brian Pratt and Keith Dewing of the Geological Survey of Canada made the discovery while exploring Victoria Island in a helicopter two years ago.
At the time, they were doing map work for a Natural Resources Canada energy and minerals program.
"It was one of the few parts of the Arctic that hasn't been mapped in real detail. There was a map done in the 1960s but it was a very general map so we were going in to make it a more detailed map," said Pratt.
"The chances of finding a new meteorite impact are a once in a lifetime thing. So you can imagine that we were absolutely thrilled that we were the lucky ones."
They say it took two years to properly confirm that it was a meteorite crater. They've produced a paper on the discovery that will now be open to peer review.
Pratt and Dewing say the crater is at least 130 million years old and could even be as old as 350 million years. They've named the new discovery the Prince Albert impact crater, after the name of the peninsula where it is located.
Pratt says it's certainly a big crater, although it's not the biggest.
According to the Geological Survey of Canada's Earth Impact Database, operated by the University of New Brunswick, one of the largest meteorite craters in Canada is at Sudbury, Ont., at approximately 130 kilometres across. The database lists a crater in Chicxulub, Mexico, as one of the largest in the world at 150 kilometres across.
Beverly Elliott, data manager at the centre, says the Chicxulub crater is the one that's thought to have wiped out the dinosaurs.
Elliott said the new crater on Victoria Island is still just a claim at this point as far as the centre is concerned. Peer review is still required before it gets on their list, she said, and it must also meet a certain number of other criteria.
"As soon as that publication comes out, we'll have a look at it," said Elliott, speaking from Fredericton.
There are at least 160 known meteorite features on Earth.
Pratt said he and Dewing knew from earlier surveys of the remote area that dipping and even vertical rock faces had been found on Victoria Island, so they wanted to check them out. Most rock in the Arctic have horizontal strata and have never been folded or faulted by tectonic pressure, Pratt explained.
He said he and Dewing set off from their camp in a helicopter with a plan to go as far northwest as they could. When they found the sloping strata, they landed and picked up the rocks. He said the very first one had cracking features called "shatter cones," which he said are telltale signs of a super-high-energy impact.
"Almost the only way you can form these things is with a meteor impact," Pratt said. "You can get small ones forming from atomic blasts but the scale we saw, it had to be from an impact."
"Something of that size could be formed by a meteorite five kilometres wide, which is pretty big. We don't get too many of those. The average sort of frequency of that kind of strike is said to be about one in every ten million years."
Pratt said they examined maps and satellite images as part of their analysis. He said there are difficulties in estimating the diameter of the crater due to erosion, noting it's even possible that the actual crater may be as big as 50 kilometres across.
He said the meteor that produced it may also have been larger, noting that if the area was covered in water at the time it hit, the impact would have been cushioned and produced a smaller crater.
Pratt said the craters add to the bank of knowledge about the history of the planet.
"It adds another piece to the cosmic puzzle of how the earth formed, and the bombardment history, and that can be compared to that of the moon or mars," Pratt said.