Two asteroids left a 400km-wide crater in Outback Australia 300 million years ago

TWO asteroids, each 10km across, slammed into Outback Australia 300 million years ago. The 400km-wide scar they left behind has just been found.

Asteroid impact

TWO asteroids, each 10km across, slammed into Outback Australia 300 million years ago. The 400km-wide scar they left behind has just been found.

Researchers from the Australian National University say the enormous impact crater this event generated has long since eroded. But it left a bruise which still extends deep into the earth.

It’s believed to be the most powerful asteroid impact yet discovered on Earth.

The crates make the Chicxulub crater in Mexico — believed responsible for the extinction of the dinosaurs some 66 million years ago — look like a minor flesh wound. It’s “only” 180km across.

Dr Andrew Glikson from the School of Archaeology and Anthropology said the impact zone near the borders of South Australia, Queensland and the Northern Territory, was discovered while drilling 2km into the earth’s crust for a completely different purpose — geothermal research.

Deep impact ... Magnetic modelling of the Warburton Basin shows the impact points of two 10km-wide asteroids. Source: ANU

“The two asteroids must each have been over 10 kilometres across — it would have been curtains for many life species on the planet at the time,” said Dr Glikson.

But exactly what that time was is a point of contention.

Rocks in the surrounding areas of the Warburton Basin have been dated between 300 and 600 million years old. But no sediment layer from the world-spanning ash cloud such an event must have generated has yet been identified.

“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,” Dr Glikson said.

Earth-shattering ... How the planet may have looked 300 million years ago, about the time of the asteroid impact. Source: Supplied

But the study, published in the journal Tectonophysics, says the deep geothermal drilling operation has uncovered unmistakable signs of a deep impact: rocks turned to glass by such an impact’s extreme heat and pressure.

Follow-up magnetic modelling in the area found the outlines of two 400km wide “bulges”.

“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,” Dr Glikson said.

“Large impacts like these may have had a far more significant role in the Earth’s evolution than previously thought.”

@JamieSeidel