Friday , January 27 2023

Asteroids increase three times over the last 300 million years Science



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The rate at which asteroids hit Earth has tripled almost from the beginning of the baby's dinosaurs, according to a study of scars left behind.

Researchers have developed the asteroid strikes on the Moon and Earth and have found that over the last 290 million years, the number of collisions has increased dramatically.

Prior to this period, the planet suffered an asteroid blow approximately every 3m years, but since then the rate has risen to almost every 1m. Figures are based on collisions that have left craters at least 10 km (6.2 miles) wide.

Graph

"The crater rate is changing instantly," said Thomas Gernon, a Southampton University scientist and colleague at the Turing Institute. "There is an order of two to three increases in the asteroids strikes of 290 million years ago."

The findings suggest that dinosaurs may have been unhappy with the evolution 240 million years ago, just as the chances of being wiped out by an alien asteroid have increased. This was one of these effects, in addition to other factors, what he did for beasts 66 million years ago.

Many scientists have assumed that asteroids strikes were a rare but constant threat in the deep history of Earth, but the latest study provokes this belief. "I was surprised to see the change," said Rebecca Ghent, a planetary scientist at the University of Toronto. "There was no reason to believe that the rate would be higher than in the past."

Writing in the journal Science, researchers describe how they returned to the moon to examine the violent history of the Earth. Earth and moon are hit by asteroids at a similar frequency, but Earth impact craters are often erased or hidden by erosion and continents that change the shell. On a geologically inactive month, impact craters are preserved almost indefinitely, making them easier to examine.

Using the images from the Navi Lunar Reconnaissance Orbiter, the scientists studied the "rockiness" of the debris surrounding the craters on the Moon. The stones thrown by the impacts of the asteroid are constantly flattened by the constant rain of the micrometeorites that flow over the moon. This means that the state of the rocks around a crater can be used up to that date.

"When you have a fresh impact, you will get a lot of large rocks around the crater, but in time they will be bombarded by small micometeorites and will be turned into a regolith of the moon," said Sara Mazrouei, the first author of the paper and a planetary scientist from Toronto.

The data showed that the moon and, by extension, the Earth, underwent a more intense asteroid bombardment in the last 290 million years, compared to any other moment in the previous billion. There are not nearly 650 million years of impact craters on Earth, most likely because they were eroded when the planet became frozen in an event known as Snow Earth.

Christian Köberl, general manager of the Museum of Natural History in Vienna – who was not involved in the study, said that although for the last several hundred million years there have been asteroid increases, the lack of craters on Earth 650m "must be home due to terrestrial geological processes."

1 billion years of monthly impact on music. Credit: SystemSounds

William Bottke, research scientist at the Southwest Research Institute in Colorado, said the asteroid blow was probably caused by one or more huge space rocks that break into the main asteroid belt between Mars and Jupiter now 300 millions of years.

When asteroids collide, they produce a swarm of fragments that can find their way to collision courses with the Earth or the moon. "If the initial collapse is large enough, the impact may last for hundreds of millions of years," he said.

The question now is whether the asteroid blow rate is still rising, or maybe it is returning to a lower level. Anyway, Ghent thinks there is no reason to alarm. "Because large impacts are very rare, first, even if you double or triple the likelihood that they are still very rare," she said.

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