Giant crater may have been extinction trigger
SYDNEY: One of the largest meteorite impacts in the world has been discovered in the Australian outback - an impact so powerful it may have been the trigger for a major extinction event.
The meteorite struck Australia around 300 million years ago and produced a 'shock zone' - the area of land deformed by the strike - at least 80 km wide.
Discovered by geothermal researchers, it is now buried deep under sedimentary rock. While the crater itself has probably eroded away, the land still bears the scars of the impact.
"This impact structure is likely to prove one of the largest found on Earth, as its minimum diameter is 80 km and its likely size larger than 160 km," said Andrew Glikson, an earth and palaeoclimate scientist at the Australian National University in Canberra.
Glikson will present the results at the Australian Geothermal Energy Conference in Adelaide in mid November.
The site was discovered when geothermal energy researcher Tonguç Uysal, from the University of Queensland in Brisbane, was looking at the processes involved in thermal enrichment in the Cooper Basin, on the border of Queensland and South Australia.
Uysal said he noticed that "[the] quartz grains in the rock had unusual planar deformation feature." This rock feature is only ever associated with the extreme pressures involved in a large asteroid strike.
More research is needed to determine both the maximum crater size and the size of the asteroid itself, said Glikson. However, the 360-milion-year-old Woodleigh crater, in Western Australia, measures somewhere between 60 and 160 km across and "was produced by an asteroid six to 12 km across," said Glikson.
The impact would have been impressive, producing "catastrophic effects - including a fireball, major earthquakes, atmospheric clouding, CO2 release, tsunami effects, [and] the extinction of species," added Glikson.
Global kill event
"This is very exciting," said Andy Tomkins, a geologist at Monash University in Melbourne, who was not involved in the study. "Only the extreme pressure associated with the impact of a large asteroid can produce these features.
"Nothing within a few hundred kilometres of the blast would have survived, but more importantly the climate of the entire Earth would have been changed. It would have filled the atmosphere with so much dust that sunlight would be obscured, possibly for several years, killing a large amount of plant life on which animals obviously rely, thereby causing a global kill event - although perhaps not on the scale of the impact that wiped out the dinosaurs.
"If such an impact occurred now, the majority of the human population would be wiped out, through the consequent reduction in our ability to grow crops," he added.
Until now Australia had 30 definitively identified impact craters, seven that lack conclusive evidence and around 12 that are being investigated.
At 80 km, it will still be the eighth largest known crater, although researchers think it may end up being even larger.
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