A 300-million-year-old ancient asteroid impact zone measuring about 200 kilometres was discovered by researchers at the Australian National University (ANU) and University of Queensland. Located at the East Warburton Basin in north-eastern South Australia, the crater is evidence of an asteroid hit on Earth.
The asteroid is believed to be over 20 kilometres wide, according to the report of the authors published in the latest edition of Tectonophysics journal. The impact zone was buried under more than two miles of dirt, said Dr Andrew Glikson, co-author of the study and a visiting fellow to the ANU Planetary Science Institute.
"It's significant because it's so large. It's the third largest impact terrain anywhere on Earth found to date . . . It's likely to be part of a particular cluster that was linked with a mass extinction event at that time," The Conservation quoted Mr Glikson.
The team took over 200 samples from the crater and studied the quartz grains to seek seismic anomalies below the Earth's surface. They believe the asteroid that created the crater split in half before it collided with the Earth's surface.
Mr Glikson said the dust and greenhouse gases that were released from the crater, the seismic shock and the initial fireball would have burned large parts of the planet, while the greenhouse gases probably stayed in the atmosphere for tens of thousands of years.
He added that based on the estimate of 280 to 360 million years the asteroid hit happened, the event would belong to the Devonian mass extinction event, part of the mass extinction caused by an impact winter with the asteroid flash, major fires and seismic events with magnitudes of 10, 11 and 12 which probably disrupted habitats.
The largest impact crater on record is the Vredefort crater in South Africa which measures 298 kilometres, followed by the Sundbury crater in Canada at 250 kilometres.
He said they initially thought the rocks recovered from drill holes intended for research into geothermal energy were volcanic in origin, but ruled it out because shocks of that magnitude could only come from a large asteroid that hit the Earth's crust.
There is an estimated 180 asteroid hit sites across the Earth and more than 30 are found in Australia. Mr Glikson tackled the asteroid impact history of Australian in 2010 in this video.
On Friday, another one was also created when the 2012 DA14, a 45-metre wide asteroid, passed just 34,000 kilometres from Earth.
On the same day, a meteorite hit Russia's Urals region and caused damaged to the area and injury to about 1,000 residents.