Like 47 Million Hiroshima Bombs: Giant Crater From Major Meteor Impact Discovered In Greenland

An international team of scientists has uncovered a vast, 19-mile-wide impact crater hidden deep below the ice sheets of Greenland.

The crater—which is bigger than the city of Paris—is thought to have been produced by a kilometer-wide (0.6 mile-wide) iron meteorite that collided with the Earth somewhere between 3 million and 12,000 years ago, although it has not been directly dated yet.

Located underneath the Hiawatha Glacier in the northwest of the massive island, the impact crater is the first to be found underneath one of Earth's continental ice sheets" according to a paper published in the journal Science Advances. In terms of size, it ranks among the 30 largest impact craters in the world, according to the researchers.

The team, led by scientists from the Centre for GeoGenetics (CGG) at the Natural History Museum of Denmark, University of Copenhagen, suggested that the meteorite struck the island before it was covered in ice 1-kilometer thick. This ice has long preserved the secrets of the catastrophic event, which would have likely had significant implications for life on Earth at the time.

"The energy released during the impact was equivalent to 47 million Hiroshima bombs," Nicolaj Larsen, a lead author of the study from the CGG, told Newsweek. "The effect on the environment would have been massive both locally in northwest Greenland but also globally. Dust from the impact and water from melting the ice sheet could have caused a global cooling event."

The team discovered the crater in July 2015 while they were examining a new map of the land and physical features below Greenland's ice sheets. In the map, they noticed an enormous "circular depression" that had previously escaped detection.

Intrigued by what they had found, the team commissioned a research plane to fly over the glacier and carry out state-of-the-art ice radar measurements. These revealed the shape of the crater in finer detail.

The next step was to try to determine what object had produced such a vast feature. To do this, the researchers chemically analyzed sediments in meltwater that had been washed out of the depression in order to look for signs of platinum, palladium, rhodium and gold, as well as other metals, which indicate a meteorite strike.

According to Larsen, some of the quartz sand washed from the crater had deformation features that suggested it was formed by a violent meteorite impact.

"The evidence is very solid," he said. "We have ice radar data which clearly show a large 31-kilometer [19.26 mile] circular depression, around 300 meters [984 feet] deep and with an elevated rim and central cone. In addition, we have found mineral grains such as shocked quartz, which is indicative of a meteorite impact."

Some of the chemical analysis results were unexpected said Iain McDonald, a co-author of the study from Cardiff University's School of Earth and Ocean Sciences, in a statement.

"Initially we thought we might find the signature from a chondritic or 'stony' meteorite but the only explanation for the pattern of metals that we found had to be a mixture between the crustal rocks in the surrounding area and an unusual iron asteroid," he said.

Several iron meteorites—including a 20 metric ton fragment known as Ahnighito—have been found in the area around Cape York, near the site of the newly uncovered crater. This indicated to the team that an impact must have occurred in the region, but until now, they had found no evidence to support the hypothesis.

Iron meteorites originate from the metal cores of asteroids or minor planets that suffered catastrophic collisions during the early history of the solar system.

"The signature we identified was not exactly the same as the [20 metric ton] iron meteorite previously found at Cape York," McDonald said.

This finding has led the researchers to suggest that Ahnighito and the samples they examined for the latest study likely represent different fragments of a larger meteorite.

"We suspect these initially detached in Earth's gravity field and then decelerated as they entered the atmosphere to fall south of the Hiawatha crater," McDonald said.

According to the researchers, the crater is exceptionally well-preserved, which is surprising given that glacier ice can be incredibly erosive and could have quickly removed any traces of its existence. This indicates that it is relatively young from a geological perspective.

"The next step in the investigation will be to confidently date the impact," Kurt H. Kjær, also from the CGG, said in the statement. "This will be a challenge because it will probably require recovering material that melted during the impact from the bottom of the structure, but this is crucial if we are to understand how the Hiawatha impact affected life on Earth."