Earth under fire: The impact of asteroids is becoming more common



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By Till Mundzeck, dpa

Toronto – The fire of Earth's asteroids has doubled to nearly three hundred million years ago. The researchers from the analysis of the impact crater age on the moon concluded that. Scientists around Sara Mazrouei from the University of Toronto (Canada) work in US journals "science"Previously, the reason for the increase was therefore unclear.

For a long time, researchers have studied the frequency of asteroid impacts in the course of Earth's history. This is not easy because tectonic plates and erosion can make the crater disappear over time. Therefore the team analyzes celestial bodies which have the same probability of impact as Earth, but there are no tectonic plates and little erosion – months. "The only obstacle is finding the right way to date a large crater on the moon," said co-author William Bottke of the Southwest Research Institute in Boulder, Colorado.

"Young" impact crater on the moon.

– Ernie Wright, NASA Goddard / dpa

Measurements with a moon probe "Lunar Reconnaissance Orbiter"

Scientists have now succeeded: with the investigation of the Lunar Reconnaissance Orbiter (LRO) moon of the US space agency NASA, they measured the heat radiation from our satellite collision crater during moonlit nights. Large stones are warmer than finely ground material. This in turn allows for conclusions about the age of the crater, because the younger craters are larger chunks, because they are more than millions of years old by micro-meteorite rains that are constantly from space gradually grinding.

Thus, the researchers date all the major moon craters that have emerged in the past billion years. Temporary distribution brings a surprise: 290 million years ago, the level of asteroid impact suddenly rose to two to three times. The same applies to Earth, which also has fewer old craters than younger ones. "This study reveals that Earth has fewer older craters on dense terrain due to erosion, but because the frequency of attacks is lower by 290 million last year," Bottke explained.

Graph showing an increase in the level of impact on the Moon and Earth.

Graph showing an increase in the level of impact on the Moon and Earth.

– Dr. R. Ghent, University of Toro

There is no explanation for the increase

Why the frequency of the impact of asteroids suddenly increased at that time, researchers have not been able to explain. It is possible that a large collision in the asteroid belt between Mars and Jupiter has sent more asteroids falling to earth, they speculated. "We can now use this technique to examine the surface of other planets to see if they also have a greater impact," Bottke said.

This finding also has implications for the history of life on Earth, which was broken down by the events of mass extinction and the evolution of fast new species: "Although the driving force behind this event is complicated, the asteroid impact certainly has a role to play in this ongoing story. "

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