Chuck Bednar for redOrbit.com – @BednarChuck
A nearly 250 mile (400 km) wide impact zone recently discovered in Central Australia is being called the largest asteroid-caused crater ever discovered, according to research published earlier this month in the international earth sciences journal Tectonophysics.
The impact craters were discovered hidden deep beneath the Earth’s crust by geophysicists from the Australian National University’s School of Archaeology and Anthropology, and according to Discovery News, they were caused by the most powerful asteroid impact ever discovered.
Lead investigator Dr. Andrew Glikson and his colleagues believe that the craters were created by a massive asteroid that broke into two pieces just prior to making impact, and the force generated by its violent collision likely had a devastating impact on creatures living at the time.
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“The two asteroids must each have been over 10 kilometers across – it would have been curtains for many life species on the planet at the time,” explained Dr. Glikson, who is also affiliated with the ANU Planetary Science Institute. He added that “large impacts like these may have had a far more significant role in the Earth’s evolution than previously thought.”
A bit of a mystery
While the impact crater itself is long gone, buried 19 miles (30 km) beneath the surface in rock that is at least 300 million years old, its imprint on the Earth’s crust remains, the website said. It was found in the Warburton Basin in Central Australia, in a region close to the borders of South Australia, Queensland and the Northern Territory, the researchers noted.
The asteroid believed to have caused the impact would have been far larger than the one that was responsible for the famous Chicxulub crater located beneath Mexico’s Yucatán Peninsula, which is believed to have caused the extinction of the dinosaurs more than 65 million years ago. The Warburton Basin impact zone is twice the size of the Chicxulub one, and was caused by two impactors, each about the same size as the six-mile (10 km) wide asteroid that caused the Mexican crater.
The impacts were discovered accidentally during a geothermal research project. While drilling more than a mile into the Earth’s crust, the team found traces of rocks that had been turned into glass by the extreme temperature and pressure resulting from a major impact event. A magnetic model of the deep crust there found chemical composition corresponding to that typically found in the mantle, including high amounts of iron and magnesium, the study authors said.
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After the Chicxulub impact, a huge quantity of debris was shot into the atmosphere, covering the globe in a tell-tale layer of sediment. However, no such layer has been found in relation to the Warburton Basin event, Dr. Glikson said, which leads to a bit of a mystery, as he said that there is no evidence of a mass extinction event that matches the timing of the collisions.
For that reason, he believes that the impact might even be even more than 300 million years old. The goal now is to uncover additional evidence for the impact to determine exactly when it happened and what impact it had on the planet.
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