Before trees existed, only single-celled organisms lived on Earth, while the largest asteroid to hit our planet landed near what we now know as Johannesburg, South Africa, forming the Vredefort crater. With an estimated crater size of 250-280 kilometers at the initial impact, the size of the asteroid was initially calculated to be about 15 kilometers in diameter. However, new research from the University of Rochester shows that the recalculated size is closer to 25 kilometers.
The team used a shock physics program called Simplified Arbitrary Langrangian Eulerian (iSALE) to calculate the size of the asteroid needed to make an impact on the scale of the Vredefort crater. With these calculations, they found that the original diameter estimate would produce an impact area measurement of about 172 kilometers. To reach the actual size of 250-280 kilometers, the impactor would have to be much larger.
Estimates of the impact this impact may have had on Earth’s environment may draw on what we already know about the aftermath of the Chicxulub crater impact. The Chicxulub crater, thought to be the cause of the dinosaurs’ mass extinction, was formed 66 million years ago by a 10-kilometer-wide asteroid that wiped out 75 percent of Earth’s plant and animal species.
Fortunately, there weren’t many living things about 2 billion years ago. Although not the cause of a mass extinction event, the Vredefort impact is thought to have had a greater impact on global climate than the Chicxulub impact.
The copious amounts of disturbing dust created by the asteroid’s collision may have blocked the sun for a long period of time, from hours to decades. This cloud of dust, blocking the sun’s rays, would cause the Earth’s surface temperature to cool considerably. As the dust settled, the carbon dioxide emitted from the impact would also cause the planet’s temperature to rise by several degrees.
The effects of this dimension and this time period may have an important place in advancing our understanding of the geographic order of the Earth 2 billion years ago.
By examining material ejected by the Vredeford crater impact, the researchers were able to match the samples with those collected from modern-day Karelia, Russia. It is estimated that the distance between the two land masses at the time of impact was approximately 2,000-2,500 kilometers.
In addition to helping us better understand what the planet was like 2 billion years ago, information from impacts of this magnitude will allow researchers to study the effects of other large planetary impacts and predict the potential effects of future collisions.
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