Asteroid Impacts On Earth Have Increased Over Time, Study Finds

Posted: Jan 20 2019, 12:07am CST | by , in Latest Science News


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Asteroid Impacts on Earth have Increased Over Time, Study Finds
Moon craters. Credit:Dr. A. Parker, Southwest Research Institute

The number of asteroids colliding with the Earth and Moon has increased by up to three times over 290 million years ago.

Space rocks are smashing into Earth more frequently than ever before. By analyzing NASA's Lunar Reconnaissance Orbiter data, researchers have found evidence that asteroid impacts on both Earth and the moon have increased by two to three times over the past 290 million years. The rate is significantly higher than in the previous 700 million years.

"Our research provides evidence for a dramatic change in the rate of asteroid impacts on both Earth and the Moon that occurred around the end of the Paleozoic era," said lead author Sara Mazrouei from University of Toronto (U of T). "The implication is that since that time we have been in a period of relatively high rate of asteroid impacts that is 2.6 times higher than it was prior to 290 million years ago."

Researchers have been trying to determine the rate that asteroids hit the Earth for decades. However, they suspected that most of Earth's earliest craters produced by asteroid impacts have disappeared over time due to erosion and other geologic processes, leaving a potential gap in the record. But a new research suggests that there are no missing craters on Earth.

"The relative rarity of large craters on Earth older than 290 million years and younger than 650 million years is not because we lost the craters, but because the impact rate during that time was lower than it is now.” Study co-author Rebecca Ghent said.

To determine the rate of asteroid impacts on Earth, researchers analyzed thermal data and images of moon’s surface collected by NASA's Lunar Reconnaissance Orbiter (LRO). Researchers believe that they can learn a lot about the Earth's impact history by calculating ages of craters on the Moon.

Moon is bombarded by asteroids in the same proportions as Earth. But lunar surface maintained its pristine state because it does not experience processes, like plate tectonics, that gradually worn away craters on Earth.

"The only obstacle to doing this has been finding an accurate way to date large craters on the Moon.” Co-author William Bottke from Southwest Research Institute in Boulder at Colorado said.

There was no way to determine the ages of lunar craters until NASA's Lunar Reconnaissance Orbiter started circling the Moon a decade ago. With LRO data, researchers were able to assemble a list of ages of all lunar craters younger than about a billion years. When they compared the ages and numbers of craters on the Moon to those on Earth, they found a remarkable similarity.

“It became clear that the reason why Earth has fewer older craters on its most stable regions is because the impact rate was lower up until about 290 million years ago.” Bottke said.

The reason for the increased in the impact rate is unknown but it could be linked to large collisions in the main asteroid belt that is located between the orbits of Mars and Jupiter. Researchers suggest that such collisions can create debris and send them into the inner solar system.

"This is how we know those craters represent a near-complete record," said Ghent. "The findings may also have implications for the history of life on Earth, which is punctuated by extinction events and rapid evolution of new species.”

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<a href="/latest_stories/all/all/47" rel="author">Hira Bashir</a>
The latest discoveries in science are the passion of Hira Bashir (). With years of experience, she is able to spot the most interesting new achievements of scientists around the world and cover them in easy to understand reporting.




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