An asteroid that slammed into South Africa long ago must have been at least five times bigger than that which killed off the dinosaurs, new research suggests

That’s a lot bigger than previous estimates for the impactor that created the Vredefort Crater – the world’s biggest – near Johannesburg 2 billion years ago.

The crater was previously measured at 160km across, about the same as the Chicxulub Crater in Mexico, believed to be where the dinosaur-killer landed 66 million years ago.

But Vredefort’s asteroid was likely much larger when it first formed – up to 280km – according to new geological evidence. That gives it a volume of potentially five times that of Chicxulub, maybe more.

Vredefort Crater
If you’re reading this in 2 billion BCE, perhaps avoid this bit of South Africa. (Image: NASA Earth Observatory / Lauren Dauphin / University of Rochester / Julia Joshpe)

To create a wound in the Earth this large, an asteroid would need to be up to 25/km across, experts at the University of Rochester say. 

“Understanding the largest impact structure that we have on Earth is critical,” said Natalie Allen, who’s since moved to John Hopkins University to do her PhD.

“Having access to the information provided by a structure like the Vredefort crater is a great opportunity to test our model and our understanding of the geologic evidence so we can better understand impacts on Earth and beyond.”

While the Chicxulub asteroid started fires worldwide and blanketed the Earth, blocking the sun and killing off numerous species, Vredefort’s asteroid didn’t. How? Well, it’s simple – there wasn’t anything to kill.

“Unlike the Chicxulub impact, the Vredefort impact did not leave a record of mass extinction or forest fires, given that there were only single-cell lifeforms and no trees existed 2 billion years ago,” said co-author Miki Nakajima.

“However, the impact would have affected the global climate potentially more extensively than the Chicxulub impact did.”

The Earth was likely a few degrees hotter than normal for “long period of time afterwards”, she said. 

Some of the material smashed out of the Earth ended up in modern-day Russia, which was likely a lot closer to ancient South Africa than it is now mind you.

“The current best simulations have mapped back about a billion years, and uncertainties grow larger the further back you go,” said Allen. “Clarifying evidence such as this ejecta layer mapping may allow researchers to test their models and help complete the view into the past”

The full study can be read in the Journal of Geophysical Research.

A recent study found the Chicxulub might not have been solely responsible for the end of the dinosaurs’ reign.