The crater dates back to 58 million years ago, instead of the previously proposed 13,000 years ago. Greenland shelters beneath its ice sheet the massive Hiawatha crater, also known as the Hiawatha impact crater or Hiawatha meteorite impact crater-which is 31 kilometers (19 miles) wide.
Some time in the past, an asteroid a kilometer across slammed down into Greenland at a speed at least a dozen times faster than a rifle bullet. Releasing as much energy as 15,000 times the largest nuclear weapon ever exploded on Earth, it carved out a gigantic crater now called Hiawatha Crater, and it's over 30 kilometers across.
This much is known. The big question is, when did this happen?