An asteroid 30 kilometres across smashed into Greenland three billion years ago, creating a crater that was once 25 kilometres deep and 600 kilometres wide.
That dwarfs the oldest known impact crater on Earth, the Vredefort crater in South Africa, both in age and size. The Vredefort is about two billion years old and about 300 kilometres across.
The new find is centred to the east of what is now the town of Maniitsoq on Greenland’s western coastline. What remains of the original crater is only about 100 kilometres wide.
This, according to the geologists who discovered the crater, explains why it remained undiscovered until now. Only the deepest parts of the crater survive. All the near-surface and easily recognisable features of the crater have been worn away. “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.
After three years of intensive work, Garde and his colleagues now say they have enough evidence to support their claim.