The world's oldest asteroid strike has been identified in outback Western Australia and may have helped lift the planet out of a global deep freeze known as a Snowball Earth, scientists say.
Researchers at Perth's Curtin University analysed the minerals zircon and monazite at the base of the eroded Yarrabubba crater, which were 'shock recrystallized' by the asteroid strike, to calculate its precise age for the first time.
They found the crater, which is between Sandstone and Meekatharra and has a diameter of 70km, is 2.229 billion years old - making it 200 million years older than the next oldest impact and about half the age of the Earth.
At the time, the landscape may have been ice-covered and the impact would have vaporised a large volume into the atmosphere.
"The age of the Yarrabubba impact matches the demise of a series of ancient glaciations," Associate Professor Nicholas Timms said.
"An impact into an ice-covered continent could have sent half-a-trillion tons of water vapour - an important greenhouse gas - into the atmosphere.
"This finding raises the question whether this impact may have tipped the scales enough to end glacial conditions."
Australian Associated Press