The dinosaurs’ reign on Earth was cut short when a six-mile-wide (10km) asteroid struck near modern-day Mexico. The impact triggered a planet-wide nuclear winter, wiping out two-thirds of all life on Earth in the process. Using cutting-edge 3D numerical simulations, researchers from the UK and the US have now pieced together why the impact was so deadly.
The asteroid most likely struck the planet at an angle of up to 60 degrees, releasing great amounts of debris into the atmosphere.
Lead researcher Professor Gareth Collins, of Imperial College London, said: “For the dinosaurs, the worst-case scenario is exactly what happened.
“The asteroid strike unleashed an incredible amount of climate-changing gases into the atmosphere, triggering a chain of events that led to the extinction of the dinosaurs.
“This was likely worsened by the fact that it struck at one of the deadliest possible angles.”
The research was carried out at Imperial College London and The University of Texas at Austin.
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The researchers examined the shape of the Chicxulub crater buried beneath Mexico’s Yucatan Peninsula to determine the direction and impact of the asteroid.
Professor Collins said: “Our simulations provide compelling evidence that the asteroid struck at a steep angle, perhaps 60 degrees above the horizon, and approached its target from the north-east.
“We know that this was among the worst-case scenarios for the lethality on impact, because it put more hazardous debris into the atmosphere and scattered it everywhere – the very thing that led to a nuclear winter.”
According to the expert, an impact between 45 and 60 is perfect for vapourising and spewing debris up into the atmosphere.
For the dinosaurs, the worst-case scenario is exactly what happened
Professor Gareth Collins, Imperial College London
Impacts that are shallower or much steeper, however, are less likely to have as big of an effect on the climate.
Professor Collins told BBC News: “It’s evident that the nature of the location where this event happened, together with the impact angle, made for a perfect storm.”
The findings were published today (May 27) in the journal Nature Communications.
In their study, the researchers wrote: “The asteroid impact that formed the 66 Ma Chicxulub crater had a profound and catastrophic effect on Earth’s environment, but the impact trajectory is debated.”
The aftermath of the impact rests under the Yucatan Peninsula, with the crater’s centre near the town of Chicxulub.
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The crater measures up to 111 miles (180km) across and is up to 18 miles (30km) deep.
Study co-author Dr Auriol Rae of the University of Freiburg said: “Despite being buried beneath nearly a kilometre of sedimentary rocks, it is remarkable that geophysical data reveals so much about the crater structure – enough to describe the direction and angle of the impact.”
However, it is only the third biggest impact crater on Earth.
The honour of first place goes to the Vredefort crater in South Africa, which measures about 190 miles (300km) across.
According to the US space agency NASA, impacts on the scale of the dinosaur killer occur every 50 million to 100 million years.
Fortunately, there is no asteroid or comet currently known to pose any danger to Earth.
NASA said: “Inevitably, an impact will occur that will cause local, regional, or even global damage.
“We just can’t predict exactly when such an impact will occur without having a complete catalogue of all objects passing near the Earth’s orbit.
“This is why we care about planning for planetary defence.
“What planetary defence is all about is developing all the capabilities we need to detect the possibility of potential asteroid impacts with Earth, warn of predicted impacts, and then either prevent them or mitigate their possible effects.”
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