Scientists estimate: a meteor impact destroyed most of life on Earth in the past

Science / Traces of a large meteor that hit the Earth 3.5 billion years ago have been found

Photo: St Ibn Zircon University, which shows the impact. A meteor covered the planet in dust and caused all the continents to flood

Washington. It is possible that a giant meteor that hit the Earth 3.5 billion years ago caused so much destruction that it affected the development of life. Scientists announced this at the end of the week. According to them, the meteor - twice the size of the asteroid that apparently destroyed the dinosaurs 65 million years ago - caused a thick layer of rocks to rise, threw into the air huge amounts of dust that covered the entire planet, and created a tide that flooded the area of ​​all ancient continents.

The researchers from Stanford University and the University of Louisiana - who published their findings in the journal "Science" put together pieces of evidence they found in ancient rock layers, at sites in Australia and South Africa.

"We have no idea where the collision site itself was," said Donald Lau, a professor of geology at Stanford University, who helped conduct the research. According to geologist Gary Birley from the University of Louisiana, the studied meteor was one of several that hit the Earth when it was still a young and relatively warm planet, and the only life form on it was bacteria.

"All of them were probably objects with a diameter of 50-20 kilometers," said Birley, "that is, it is about two to five times the size of the object that caused the extinction of the dinosaurs 65 million years ago." According to him, "the intensity of the vulnerability was great. They did change the course of the evolution of life on Earth." However, the study did not make any assumptions about the nature of the changes that occurred.

According to Lau, it is not clear what the impact of the vulnerability was on the bacteria, whose development was then in full swing. Unlike larger animals such as dinosaurs, bacteria can survive even in extreme conditions. Today, bacteria can also be found deep in the oceans in places where light does not reach them; in the depths of the earth; In the ice of the South Pole and sulfur springs. However, Law points out: "There is no large-scale extinction event that can be pointed to that is as sharp and clear as that of the disappearance of the dinosaurs."

The sediment layers in which the research was carried out were found in the "Greenstone" belt of South Africa and the "Pilbara" block of Western Australia. Both sites contain rocks that were formed more than three billion years ago, when the earth was only a billion years old. These deposits contain zircon stones and rare metals, such as iridium.
According to Birley, "Zircon is the geologist's best friend. It is very resistant to changes and contains information about the age of objects that may be as old as the solar system itself."

Using special equipment, the zircons were dated, and found to be 3.47 billion years old. "We can investigate these events, which took place a long time ago, by going to a limited number of places on Earth where there are sufficiently old rocks," Birley said.

According to Birley and Law, the asteroid hit a planet that was very different from the Earth we know today. "Apparently there were no large landmasses then," said Lau, "but there were many 'microcontinents', very small, exposed pieces of the Earth's crust."