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The largest asteroid to ever hit Earth, which slammed into the planet about 2 billion years ago, may have been even more massive than scientists previously thought. Based on the size of Vredefort Crater, the enormous impact scar left by the gigantic space rock in modern-day South Africa, researchers recently estimated that the epic impact crater may have been about twice as wide as that asteroid that wiped out the Nonavian dinosaur.
Vredefort Crater, located about 75 miles (120 kilometers) southwest of Johannesburg, currently measures about 99 miles (159 kilometers) in diameter, making it the largest visible crater on Earth. It’s smaller, however, than the Chicxulub crater buried beneath Mexico’s Yucatán Peninsula, which measures about 180 km in diameter and was left behind by the dinosaur-killing asteroid that impacted Earth At the end of Cretaceous about 66 million years ago.
But impact craters slowly erode over time, causing them to shrink. The latest estimates suggest that Vredefort Crater was originally 155 to 174 miles (250 to 280 km) in diameter when it formed 2 billion years ago. As a result, the Vredefort crater is considered the Largest impact crater on earth although it is smaller than today’s Chicxulub crater.
In the past, scientists thought the Vredefort crater was originally much smaller – about 172 km wide. Based on this estimate, researchers previously calculated that the asteroid responsible for the impact would have been about 15 km (9.3 miles) in diameter and collided at a speed of about 53,900 km/h (33,500 mph). But in a new study, scientists have re-examined measurements of the crater and gained new insight into the size of the giant space rock.
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In the study, published online Aug. 8 in Journal of Geophysical Research: Planets (opens in new tab)The researchers recalculated the size of the asteroid Vredefort and found that the destructive space rock was likely between 20 and 25 km (12.4 and 15.5 miles) in diameter and traveling between 72,000 and 90,000 km/h (45,000 and 56,000 mph ) might have moved. when it hit our planet.
“Understanding the largest impact structure we have on Earth is critical” because it allows researchers to create more accurate geological models, says the study’s lead author Natalie Allen, a doctoral student in the Department of Physics and Astronomy at Johns Hopkins University Baltimore, out. said in a statement (opens in new tab). More accurate predictions of impactor sizes could also shed light on other craters on Earth and around the world solar systemShe added.
size uncertainty
In the past, scientists have had difficulty determining the original size of Vredefort Crater due to its erosion over the past 2 billion years.
To understand how erosion affects old impact craters like Vredefort, imagine you’re continuously clipping the rim of a bowl, said Roger Gibson, a structural geologist at the University of the Witwatersrand in South Africa who is not involved in the study was NASA’s Earth Observatory (opens in new tab) in 2018. “If you sliced horizontally through the bowl incrementally, you would see that the diameter of the bowl decreased with each slice you took off.”
In addition to the natural erosion of the Vredefort impact structure, newer rock formations have formed on parts of the crater, the researchers wrote. As a result, most of the crater’s original structure was completely covered by younger rocks and only small sections of the raised crater rim are visible today, making it even more difficult to tell how large the crater once was.
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However, other recent studies have estimated the size of Vredefort Crater by focusing on minerals surrounding the crater. In this way, scientists have detected deformations and shock fractures in crystals such as quartz and zircon caused by the ancient impact, thereby expanding the known radius of the blast, the study authors wrote.
As a result, researchers are confident that their new estimate for the size of asteroid Vredefort is more accurate than previous estimates.
A disastrous effect
If the Dinosaur Killing Asteroid, which was probably about 12 km wide, hit Earth about 66 million years ago, the destruction caused by the impact was immense. The late Cretaceous event caused widespread wildfires and acid rain. kilometers high waves a tsunami that reached halfway across the planet; and sent clouds of ash and dust into the atmosphere, drastically changing the climate. Around 75% of life on Earth was wiped out by the event, according to a study published in the Journal in December 2021 Scientific Reports (opens in new tab).
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Based on revised calculations of Vredefort Crater’s original size, the new study suggests that the Vredefort asteroid was likely about twice the size of the dinosaur-killer. It could also have traveled much faster, so its impact would have been even more severe — possibly the largest single energy-release event in Earth’s history, the study authors reported. However, since the impact was so long ago, there is little evidence of the shattering force of the blast and the impact of the collision on the planet.
“Unlike the Chicxulub impact, the Vredefort impact left no record of mass extinctions or wildfires because two billion years ago there were only unicellular life forms and no trees existed,” said study co-author Miki Nakajima, a planetary scientist at the University of Rochester in New York said in the statement. “However, the impact would have potentially had a greater impact on global climate than the Chicxulub impact.”
Therefore, further study of the Vredefort crater may be the only way researchers learn more about these catastrophic impacts.
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