Scientists at Curtin University have discovered that a crater in Yarrabubba, Western Australia, may be the world’s oldest, and that the asteroid’s landing 2.2 billion years ago may one of the reasons behind the end of the last Ice Age.
Despite the crater itself having been discovered in the outback in 1979, scientist had previously not tested the mineral deposits left behind to determine its age. The crater is not visible to the naked eye due to billions of years of erosion.
To determine when the asteroid hit the earth, scientists tested tiny zircon and monazite crystals found within the rocks whose properties will have changed upon the impact. Tiny amounts of uranium and iron deposits within the crystals enabled the scientists to figure out relatively accurately how long ago the asteroid struck.
The team of scientist are very excited about the age of the crater especially in the context of the Earth’s other events.
At this point, 2.2 billion years ago, the Earth’s surface was covered in ice, and it is now believed that the water vapour produced by this asteroid striking such a thick sheet of ice could be the reason behind a warming effect on the planet, perhaps even ending the Ice Age. Water vapor today is the most abundant greenhouse gas within the Earth’s atmosphere. Without greenhouse gasses, it is estimated that the average temperature of the planet would be -18 degrees Celsius, rather than the 15 degrees Celsius that currently stands. With additional greenhouse gasses entering the atmosphere, the average temperature of the planet is set to continue to rise.
Other theories have suggested that the carbon dioxide, another greenhouse gas, released from volcanic eruptions may be responsible.
Main Image: Barlangi Hill, part of the Yarrabubba crater. Graeme Churchyard, Flickr Creative Commons