Aussie Impact Crater
© NASA Earth Observatory
Another major Australian asteroid impact site at Gosses Bluff in the Northern Territory.
Australian researchers have found evidence of a major asteroid impact that occurred near the Queensland-South Australia border more than 300 million years ago.

The asteroid, which produced a "shock zone" at least 80 km wide, could be the second-largest impact ever found in Australia.

University of Queensland geothermal energy researcher Dr Tonguc Uysal discovered the evidence of the impact during his studies of the Cooper Basin, which is a large geothermal energy resource being developed on the border between Queensland and South Australia.

Unusual deformations

"I noticed that the quartz grains in the rock had unusual deformation features that indicated either it had been exposed to extreme tectonic pressure or a large asteroid impact," Tonguc says. "The rock deformations were confirmed as being the result of an asteroid impact through microscopic examination of the quartz crystals and further laboratory tests."

"The results suggest that either a very large asteroid or a cluster of asteroids landed, but we need to do further testing to verify this," he adds.

Along with Dr Andrew Glikson of the Australian National University, Tonguc will present his findings at the Australian Geothermal Energy Conference in Adelaide starting on 19 November.

Boiling ground water

Tonguc says the impact of the asteroid likely triggered a huge explosion and caused the ground water to boil and induce chemical and mineralogical changes in the surrounding rocks.

"This may have resulted in the reconcentration of various heat-producing elements which has made the Cooper Basin such a rich source of geothermal energy today," he says.

The land surface that the asteroid hit is now buried deep under layers of sedimentary rock and the researchers think the original crater has most likely eroded away. Further studies of rock samples from drill holes in the Cooper Basin will be required to more accurately map the extent of the impact area and allow scientists to estimate the size of the asteroid.

Australia's largest recorded asteroid impact is at Woodleigh, east of Shark Bay in Western Australia. The Woodleigh impact structure is 120 km in diameter and was produced by an asteroid 6 to 12 km across, about 360 million years ago.