Earth’s Most Powerful Asteroid Impact Discovered In Outback Australia

Two asteroids about ten kilometres, or a bit over six miles, wide are believed to have cannoned in to what is now the dry Australian Outback, about three hundred million years ago or even longer. Although the crater which formed as a result of the impact has been long eroded, scientists from the Australian National University in Canberra, say what they have found is a bruise extending far beneath the Earth’s surface, which remains proof of the impact.

It is now believed to be the most powerful asteroid impact that we have ever managed to find. Previously, the Chicxulub crater in Mexico had been the largest evidence of an asteroid impact. This impact is believed to have been responsible for the Cretaceous–Paleogene extinction event (the one that killed the dinosaurs) about sixty-six million years ago. In terms of size however, Chicxulub is 180 kilometres, or just under 112 miles, across whilst the new found evidence extends across a width of 400 kilometres, or 250 miles.

The discovery was made inadvertently. There was geothermal research being conducted near the borders of the Australian states of Queensland, South Australia, and the Northern Territory. The project required the researchers to rill about two kilometres in the Earth’s crust, and it was upon analysis that they realised what they had found.

There remains some contention over just when the impact would have taken place with some suggesting that three hundred million years ago is too recent after considering a few factors. But there can be no denying what it would have meant for the species of Earth during that time.

“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 Andrew Glikson from ANU’s School of Archaeology and Anthropology, according to news.com.au.

It is interesting to note that rocks found in the surrounding areas are dated anywhere between three hundred million years ago and six hundred. Scientists, whilst excited by the find, are somewhat puzzled with regards to pinning an exact time on the impact; they have as yet been unable to find a sediment layer left behind from what would have no doubt been a globe-spanning ash cloud.

“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.

The results of the study have been published in the journal Tectonophysics, and conclude that despite the fact that certain things are uncertain, what is definite is the existence of the asteroid impact itself. One of the most compelling pieces of evidence that point toward the impact is the existence of some rocks turned to glass through the extreme heat such an impact would result in.

Magnetic modelling techniques were used to follow up the find in the area and showed the 400 kilometre wide impact 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,” says Dr Glikson. “Large impacts like these may have had a far more significant role in the Earth’s evolution than previously thought”.