A team of geologists from Curtin University has discovered unequivocal evidence for a hypervelocity meteorite impact 3.47 billion years ago (Archean Eon) in the center of the Pilbara region in Western Australia. Before this discovery, the oldest impact crater was 2.2 billion years old, so this is by far the oldest known crater ever found on Earth.
“With more than a million craters exceeding 1 km in diameter, and around forty more than 100 km across, the Moon preserves an exquisite record of the intense bombardment endured by bodies in the inner Solar System during the first billion years or so of its history,” said Curtin University’s Professor Tim Johnson and his colleagues.
“On Earth, this early impact record has seemingly been lost, reflecting the destructive efficiency of erosion and subduction in recycling primary crust back into the convecting mantle.”
“Nevertheless, the oldest parts of many cratons, the ancient Archean (4 to 2.5 billion years ago) nuclei of the continents, formed at or before 3.5 billion years ago, and should preserve some evidence for an impact flux that would have exceeded that of a similar area of the Moon of comparable age.”
“However, the oldest recognized terrestrial impact structure, at Yarrabubba, Western Australia, is dated at 2.23 billion years ago. Where are all the Archean craters?”
Professor Johnson and co-authors investigated Archean rock layers at the North Pole Dome in the Pilbara region and found evidence of a major meteorite impact 3.5 billion years ago.
“The discovery significantly challenged previous assumptions about our planet’s ancient history,” Professor Johnson said.
The researchers discovered the Archean crater thanks to shatter cones, distinctive rock formations only formed under the intense pressure of a meteorite strike.
The shatter cones at the site, about 40 km west of Marble Bar, were formed when a meteorite slammed into the area at more than 36,000 km/h.
This would have been…
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