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spaceSpace and Physics

Where Have All Earth's Impact Craters Gone?

author

Josh Davis

Staff Writer

clockJun 29 2015, 16:12 UTC
793 Where Have All Earth's Impact Craters Gone?
Action Sports Photography/Shutterstock

Despite being half the size of Earth, the Red Planet has a staggering 300,000 impact craters littering its surface. Compare this with the paltry 128 that scientists have managed to find on our planet's exterior, and you have to wonder why there’s such a big difference. Is it because they get worn away on our planet quicker than on Mars, or do we simply need to look harder?

A new study, carried out by researchers at the University of Freiburg, has concluded that this meager number is not due to poor search efforts but fairly accurately reflects the number that should be expected for the work put in, and that all of the big impact craters have already been found. They estimate that while all craters above 6 kilometers (3.7 miles) in diameter have been documented, there are still some 350 smaller ones hiding out there. This is still significantly fewer than what we see on Mars, which the researchers conclude is attributable to erosion by wind and rain. 

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“I'm definitely surprised,” Brandon Johnson, a planetary scientist who was not involved in the study, told Science. “It’s the first time anyone has done this kind of thing – taking into account the effects of erosion.”

By combining the estimates of impact crater numbers and the known rates of erosion, the scientists were able to produce the most accurate prediction yet for the number of craters to be expected. The results, to be published in Earth and Planetary Science Letters, suggest that researchers should stop looking for larger impact sites and should instead start looking for the smaller ones. But we shouldn’t just be looking at past events. At some point, there will be another strike.

Experts put the odds of a 100-megaton asteroid hitting Earth in your lifetime somewhere in the same ballpark as you having a car accident on a given day. Not massively high, but at the same time, high enough to make you wear your seat belt. This has led to a group of experts, scientists and filmmakers creating Asteroid Day, a global awareness campaign to encourage people from all around the world to get together and talk about the large lumps of rock hurtling through space and the threat that they pose to our planet.

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It’s estimated that there may be more than a million asteroids that could hit our planet with devastating effect, and yet we know about just 1% of those whizzing around our solar system at the moment. Because of this, there is a call to action to sign the 100x declaration, to get more research and funding invested not just into the detection of asteroids, but into new technology to help to protect the Earth from such potential collisions. 


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