One of the largest ancient asteroid impact zones on Earth has been discovered in the Australian outback, scientists say.

Researchers from the Australian National University and University of Queensland said the impact zone in northeastern South Australia was caused by an asteroid up to 12 miles wide crashing into the planet between 298 and 360 million years ago, the Australian Broadcasting Corp. reported.

The landscape around the impact site shows evidence of changes caused by shock-wave related deformation, they said.

"This shock metamorphic terrain covers an area of over 30,000 square kilometers (12,000 square miles) making it the third-largest site of its kind ever discovered on Earth," Andrew Glikson from the Australian National University said.

Microscopic examination of quartz grains retrieved from drill holes revealed tiny fractures, indicating the grains had been shocked by an asteroid or meteor impact.

"This is the only way these features are formed," Glikson said.