Evidence suggesting that the 70-km wide Yarrabubba crater in Western Australia may be Earth’s oldest preserved impact structure by over 200 million years is detailed in a paper published in Nature Communications. Geological dating of shocked minerals within the crater reveals that a meteorite hit the site 2.229 billion years ago.
The Earth has a continually changing surface due to tectonics and erosion, which means that very old impact craters are difficult to identify. Although impact ejecta material older than two billion years has previously been reported and dated in parts of Australia and Africa, the corresponding impact craters could not be identified. The Yarrabubba impact structure is regarded as one of Earth’s oldest, but until now has lacked a precise age.
Timmons Erickson and colleagues analysed shock-recrystallized minerals within the Yarrabubba impact structure, which reveal a precise age for the impact event: 2.229 billion years ± 5 million years. The authors note that this new date for Yarrabubba coincides with a period of glaciation in the same region. Numerical impact simulations reveal that if the Yarrabubba-forming meteorite collided into a continental ice sheet, it could have released between 87 trillion and 5,000 trillion kilograms of water vapour into the atmosphere, potentially playing a role in modifying Earth’s climate.
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