The meteorite that caused the crater would have to be 19 miles wide. (Photo : Wikimedia Commons)
After three years of intense work, a team of scientists have uncovered the biggest impact crater on our planet in Greenland. To find the next biggest, you'd have to travel to the moon or Mars.
The crater is approximately 62 miles wide and three billion years old. This makes it larger and older than the previous record holder in South Africa, the Vredefort, which is half as wide and two billion years old.
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So how could something so large go unnoticed for so long? Apparently, all of the surface features have been worn away over the last three billion years, and only the deepest parts of the crater survived.
"The rocks we see today were about 25 kilometres down when the impact occurred," says Adam Garde of the Geological Survey of Denmark and Greenland in Copenhagen, Denmark, who led the team.
The cornerstone of their claim is the dispersion of the granite. The granite rocks examined hint at a massive, pulverizing impact because they are deformed and spread out over an wide area.
"You might see something similar in a geologic fault zone, but not in a circle 100 kilometres across," says team member Iain McDonald of Cardiff University.
In addition, the quartz deposits around the crater show signs of micro-fractures and other characteristics that are common in impact sites.
"The patterns conformed to what you would expect from impacts, not from those that happen through terrestrial geology," says McDonald.
There is some doubt, however, as to whether or not the findings conclusively indicate a crater.
Not everyone is completely convinced that the geologists have found an impact crater.
"It points towards it being a crater, but frustratingly, I don't know if it will ever be proven," says John Spray, a specialist in impact science at the University of New Brunswick in Fredericton, Canada, who is familiar with the work. "On the other hand, I don't think anyone can definitively say it isn't a crater."