Greenland is covered with one of the largest ice sheets on the planet, but under its frozen look, the landscape is sharper than we ever thought.
Buried under two kilometers of ice, the researchers believe they have found a second massive crater hidden in the northwest corner of the world's largest island.
Since scientists are exploring more and more of our planet, new craters are more and more rarely found, especially in icy places such as Greenland or Antarctica.
In fact, before finding the first crater of Hitachi's impact in November last year, most experts simply assumed that any evidence of past impact would be erased by the relentless erosion of the ice in these regions.
So it's quite an exception that within just a few months, we have now revealed what resembles two of these rare riches, both located in Greenland.
"We have explored the Earth in many different ways, from land, air and space – exciting is that such discoveries are still possible," says co-author Joe McGregor, a NASA space flight scientist.
The discovery is made possible by a combination of satellite images and radar data, allowing researchers to "see" deep under the ice.
It was here that they noticed a circular pattern, only 183 km (114 miles) from the first crater of impact. With dimensions more than 36 kilometers (22 miles), the model has similar features to the neighboring impact crater – a concrete, flat, cup-shaped depression surrounded by a raised ridge and centrally located peaks.
Although not as clearly defined as the Hiawatha crater, if it is confirmed that this second impression is the fingerprint of a meteorite, it will be the 22nd largest crater of impact ever found on Earth – three points in front of Hiawatha.
"The only other circular structure that could reach that size would be a collapsed volcanic caldera," McGregor said.
"But areas with known volcanic activity in Greenland are a few hundred kilometers. Besides, the volcano must have a clear positive magnetic anomaly and we do not see it at all.
But even if it turns out that Khayava has a brother or sister, it is unlikely that the two craters are twins. The authors predict that the second is not only larger but also older.
Analyzing the nearby ice cores, McGregor and his team concluded that the area had not been damaged by strong force for at least 79,000 years. This may mean two things: that impact has occurred more than 79,000 years ago; or it happened sooner, and the broken ice just left.
But discovering the age of the crater is a tough business. In this case, the researchers have calculated that ice should erode the crater to its present form between 100,000 years and 100,000 years.
"The ice layers above this second crater are unmistakably older than those over Hiawatha, and the second crater is about twice as eroded," McGregor said.
"If both are formed at the same time, then perhaps thicker ice over the second crater would be equalized with the crater much faster than the Hawaiian.
Also, it is not so unusual, statistically speaking, that two different meteorites should land so close together. Two sets of neighboring craters of different ages have already been discovered in Ukraine and Canada, and computer models confirm that these events are not so unheard of in the land craters record.
"The existence of a third pair of unrelated craters is modestly surprising, but we do not think it's unlikely," says McGregor.
"In general, the evidence we have gathered shows that this new structure is very likely a shooter, but at the moment it seems unlikely to be a twin with Hawa."
This study was published in Geophysical studies,