Rock impacts from our solar system (from the asteroid belt, located between Mars and Jupiter) are frequent. Every day the Earth is bombarded by meteors, most of which disintegrate on the way into the atmosphere, long before becoming a danger to life on our planet. However, every so often (thousands of years), there is an impact by an object large enough to cause significant damage. In the past, the Earth has even suffered mass extinctions caused by the impact of large space rocks, such as the one that precipitated the disappearance of dinosaurs and other large animals 66 million years ago.
The scars of these millennial impacts are the craters , which scientists are dedicated to studying and cataloging. There are a considerable number of craters drawn on the surface of our planet, through which we can write the history of the Earth. But what is the oldest known crater?
In 2012, a group of European geologists published the discovery of the oldest impact crater on Earth in the city of Maniitsog (Greenland). It is a 100-kilometer-diameter crater caused by the fall of an asteroid 3 billion years ago. Experts had suspected the existence of the crater since 2009, when the Geological Survey of Denmark and Greenland, analyzing geological maps of the surroundings of Maniitsoq, discovered strange anomalies in the structure of the local rocks, caused by the impact of a giant meteorite. Later, new studies and new expeditions were carried out in Greenland with Russian, English and Swedish experts, in 2010 and 2011, at which time they were able to confirm that the data obtained in the area corresponds to the oldest impact crater on the planet.
The lead author of the work, Iain McDonald, indicated that this unique discovery allows studying the consequences of a meteoric bombardment of the planet that occurred a billion years earlier than previously believed. The impact that caused the crater occurred about 3 billion years ago, as can be deduced from the absence of the ‘cup’, the usual shape of craters. In addition, the calculations made allowed to conclude that the asteroid that hit the Earth was more than 30 kilometers. In this sense, the study highlights that, if such a body fell on a continent, it would have caused a funnel up to 600 kilometers in diameter, or twice that of the Vredefort crater in South Africa.
According to its discoverers, this crater was ‘hidden’ under the long glacial and mountain-building periods that Greenland has been experiencing for 3 billion years until now. As evidenced by the tests, the ice erased all the traces of the meteorite fall, except for the deformations caused in the rocks by the shock wave, which are what allowed this discovery.
Another of the oldest known craters is the crater named Yarrabubba, described in early 2020, with a diameter of 70 kilometers and an age of more than 2.229 million years.
