Scientists believe meteors may be striking Earth more frequently than thought

By Ben Mitchell, PA,
PA Media: Science•January 2, 2020

Scientists believe that meteors may be striking the Earth more often than previously thought after they found one of the world’s largest craters is 180,000 years younger than earlier estimates.

Dr Tim Barrows, from the University of Portsmouth, has used two dating techniques to establish that Wolfe Creek Crater in northern Western Australia is 120,000 years old – not the 300,000 years it was previously aged at.

He explained that the crater was most likely to have been created by a meteor about 15 metres in diameter and weighing 14,000 tonnes hitting the Earth.

For the study published in the journal Meteoritics & Planetary Science, the researchers collected samples from around the crater and used exposure dating which estimates the length of time a rock has been exposed at the Earth’s surface to cosmic radiation.

Wolfe Creek in northern Western Australia (University of Portsmouth/PA)

And they were also able to determine the age of sand buried after the impact through optically stimulated luminescence – a dating technique which measures how long ago sediment was last exposed to sunlight.

Dr Barrows, a professor of environmental change, said: “The crater is located in a fortuitous situation where we can use two different techniques to determine its age.”

Wolfe Creek Crater is one of seven sets of impact craters in Australia dating to within the last 120,000 years. From this, the researchers were able to calculate how often these crater-producing events occur.

Dr Barrows explained that the dating exercise suggested that meteors could be striking the planet more frequently than previously calculated.

He said: “Although the rate is only one large meteor hitting Australia every 17,000 years, it isn’t that simple. The craters are only found in the arid parts of Australia.

“Elsewhere, the craters are destroyed by geomorphic activity like river migration or slope processes in the mountains.

“Since Australia has an excellent preservation record with dated craters within the arid zone, we can estimate a rate for the whole Earth.

“Taking into account that arid Australia is only about 1% of the surface, the rate increases to one hitting the Earth every 180 years or so.

“There have been two big objects hitting the atmosphere in the last century – Tunguska in 1908 and Chelyabinsk in 2013.

“This is a minimum estimate because some smaller impacts were probably covered by sand during the last ice age.

“The number of large objects in the atmosphere is probably 20 times this number because stony meteorites are far more common but not as many survive the fiery journey through the atmosphere or effectively make craters.

“Our results give us a better idea of how frequent these events are.”

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