Scientists discovered a 250 mile-wide impact zone from a giant meteorite that broke into two before slamming into central Australia.
The finding marks the largest impact zone ever found on Earth, the Australian National University reported. The crater from the impact is believed to have disappeared long ago, but the deep impact evidence was discovered during drilling as part of geothermal research. The impact most likely wiped out a number of species.
"Large impacts like these may have had a far more significant role in the Earth's evolution than previously thought," said Andrew Glikson from the ANU School of Archaeology and Anthropology.
The exact date of the impact is unclear, but the surrounding rocks are between 300 and 600 million years old. Despite these facts, evidence left by other meteorites is scarce. In one example, a meteorite that hit the Earth about 66 million years ago created a plume of ash that is found in rocks around the world, this event is believed to have led to the extinction of a variety of species, including dinosaurs, but a similar layer has not been found in rocks that are about 300 million years old.
"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," Glikson said.
Magnetic modeling of deep crust in the region where the impact evidence was found revealed iron and magnesium-rich bulges of land that corresponded with the composition of the Earth's mantle.
"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," Glikson said.
