Asteroids collide with Earth twice as many times as before

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Washington- There are more asteroids colliding with the Earth than before, but this is not an alarm signal.

In the last 290 million years, large asteroids have collided with the Earth at a rate more than double 700 million years ago, according to a new study published Thursday by the journal Science.

But it's not like looking at the sky with fear. On average, asteroids collide with the Earth every million or every million years, even when the collision rate is increased. The list of major NASA steroids that could collide shows that there are no major threats to the sight. The biggest known risk is a 1.3 kilometer (4.200 ft) long asteroid with a 99.98% probability that it will not touch Earth when it passes here in 861 years.

Tell the dinosaurs. Most scientists believe that dinosaurs and many other species became extinct after a giant asteroid fell in Central America some 65 million years ago.

"It's a game of chance," said study director Sara Mazrouei, a planetary scientist at the University of Toronto. "These events are still rare and do not happen continuously."

Mazrouei and some of his colleagues in the United Kingdom and the United States have compiled a list of craters from asteroid fall on Earth and the Moon that were more than 20 kilometers (12 miles) in diameter and discovered their date of training. Holes of this size are formed by asteroids of 800 meters (half a mile) wide.

The team counted 29 craters with less than 290 million years and nine with between 291 and 650 million years.

But we can see relatively less large craters on Earth because the oceans make up more than 70% of the planet and glaciers of the past have flattened holes, said planetary scientist Rebecca Ghent of the University of Toronto, co-author of the study.

Extrapolating what can not be seen, there are a total of around 260 collisions with asteroids over the last 290 million years. Adding other factors, the scientific team has determined that the current rate of asteroids drops 2.6 times compared to the previous 700 million years.

Craters of more than 650 million years have virtually disappeared due to glacial forces, so scientists have used the number of craters formed by asteroids on the Moon as a substitute for craters formed between 650 million and 1,000 million years ago. AP

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