A large crater in northwest Greenland, buried under a thick layer of ice and first seen in 2015, has turned out to be much older than previously thought. This crater was formed by a meteorite impact 58 million years ago.
Previously, a number of researchers estimated the crater was formed about 13,000 years ago. Scientists say they used two different dating methods on the sand and rock left over from the impact to determine when the 31km wide crater formed.
They found that a meteorite about 1.5-2 km in diameter hit Greenland about 8 million years after the impact of a larger asteroid on Mexico's Yucatan Peninsula that wiped out the dinosaurs.
The crater is located under Greenland's Hiawatha Glacier, covered by a 1 km deep layer of ice. The crater remained undetected until airborne ice-penetrating radar data alerted scientists to its whereabouts.
It is one of the 25 largest known impact craters on Earth. Over thousands of years, Earth has been hit by space rocks time and time again, although gradual changes in Earth's surface have erased or obscured many craters.
Greenland then, during the Paleocene Age, was not the icy place it is today. On the other hand, Greenland is covered in temperate rain forest inhabited by various trees and inhabited by some of the mammals that became the dominant land animals on Earth after the dinosaurs went extinct.
The meteorite released millions of times more energy than an atomic bomb, leaving a crater large enough to engulf a city.
"The impact will be devastating for the local area," said geologist at the Swedish Museum of Natural History Gavin Kenny, lead author of the study published in the journal Science Advances.
"The air blast from the impact will knock down most trees within tens to hundreds of kilometers, and the thermal explosion from the impact will ignite trees hundreds of kilometers from the impact site, starting a very large forest fire," Kenny added.
He explained that the impact would also trigger regional seismic shocks. Meanwhile, ash from forest fires and dust and molten rock that have been violently ejected into the atmosphere will rain, creating a thick blanket of debris.
"Whether the impact has a long-term effect on global climate is currently unclear, but unlikely in my opinion," said geology professor and study co-author Michael Storey of the Natural History Museum of Denmark.
Some scientists have hypothesized that the impact occurred after the Greenland ice sheet formed 2.6 million years ago and perhaps even as recently as about 13,000 years ago to initiate a documented cold period.
The researchers used two dating methods based on radioactive decay, the transformation of atoms of one element into atoms of another element. Because the ice-covered crater was inaccessible, they tested the sand from the rock that was very hot by the impact and a mineral called zircon contained in the gravel. Everything is taken from the river that carries material from the crater out of the glacier. Both methods produce the same age results.
"Thus, impacts do not occur, or cause climate change events, in human times as previously predicted and speculated," said Kenny.
"An impact of this magnitude only occurs every few million years so we shouldn't be too concerned about an impact like that happening in the near future," Kenny added.