A group of researchers identified an ancient asteroid impact site in Central Australia as the largest in the world.
According to ABC News, a science team led by the Australian National University's (ANU) Andrew Glikson found two ancient craters that appears to have been caused by the same asteroid that split in two. On the surface, the craters have disappeared, so the scientists had to use geothermal drilling to find what they were looking for.
"They appear to be two large structures, with each of them approximately 200 kilometers," Glikson told ABC News. "So together, jointly they would form a 400 kilometer structure which is the biggest we know of anywhere in the world.
"The consequences are that it could have caused a large mass extinction event at the time, but we still don't know the age of this asteroid impact and we are still working on it."
The team published their work in the journal Tectonophysics.
"And what really was amazing was the size of the terrain that has been shocked. It's now a minimum of 200 kilometers (in diameter), this makes it about the third biggest anywhere in the world," Glikson told the Agence France-Presse in Feb. 2013. "Following that I spent many months in the lab doing a number of tests under the microscope to measure the crystal orientations... and determined that these rocks underwent an extraterrestrial impact or shock."
At the time, he compared the Central Australian site to the asteroid impact in Chelyabinsk, Russia. In that instance, the asteroid broke up upon entering the atmosphere, sending tiny bits of rock through windshields and windows all over. Glikson said that impact paled in comparison to his.
The study's leader said in an ANU press release each asteroid "must each have been over 10 kilometers across." He said such huge impacts likely adds to the history of the Earth's evolution.
"It's a mystery - we can't find an extinction event that matches these collisions. I have a suspicion the impact could be older than 300 million years," Gilkson said in the release. "There are two huge deep domes in the crust, formed by the Earth's crust rebounding after the huge impacts, and bringing up rock from the mantle below."
