THE world’s oldest-known crater from an asteroid smash 3.5 billion years ago has been discovered in the Australian outback.
The ancient hole, near the town of Marble Bar, north-west Australia, was 60 miles wide when first blasted into Earth’s crust.
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Scientists said it had a “global impact”, with debris strewn as far as South Africa.
Until now, a crater called Yarrabubba held the title of the oldest meteor strike site.
But the Pilbara site – dubbed the “North Pole Crater” – has steamed to the top spot, beating the competition by more than a billion years.
Today, there is still a 35km scar in the land, but – interestingly – the ground is raise rather than dipped.
Tim Johnson, a geologist and co-author of the new study, explained why.
He said: “So, when you form a really big crater, the middle bit forces it’s way back to the surface so you get a dome structure.”
Professor Johnson and his team have held for years that there was a massive meteor impact around 3.6 billion years ago in the area.
They called the region in north-west Australia the Pilbara Craton – and visited to try and back up their theory.
After just an hour on site, they came across rock structures called “shatter cones” – proving them right.
Johnson said: “They’re these beautiful, delicate little structures that look a little bit like an inverted badminton shuttle cock with the top knocked off.
“So, upward facing cones with delicate feathery-like features.
“The only way you can form those in natural rocks is from a large meteorite impact.”
Research by the Geological Survey of Western Australia dated the rock around the shatter cones as 3.47 billion years old.
Tim Barrows, a scientist at the University of New South Wales, said the “exciting discovery” of shatter cones proved beyond doubt that a meteor had struck.
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He said: “It would be near the diameter of the impact that resulted in the extinction of the dinosaurs, Chicxulub crater, which is the second-largest impact structure on Earth.
“So, it is likely to have had a global impact.”
The scientist also said that solidified molten droplets – known as spherules – would have showered the air, possibly falling as far as South Africa.
Earth was formed around 4.5 billion years ago, and the meteor smashed into Pilbara around a million years later.
There is very little evidence of meteor impacts in the first half of Earth’s life time – making Pilbara a rare find.
This impact happened during the Archaean eon – the time period from 4 billion to 2.5 billion years ago.
During that time, our planet was mostly water.
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