Rochester researchers have provided a more accurate simulation of the impact that formed Earth糖心传媒檚 largest crater two billion years ago.
About two billion years ago, an impactor hurtled toward Earth, crashing into the planet in an area near present-day Johannesburg, South Africa. The impactor糖心传媒攎ost likely an asteroid糖心传媒攆ormed what is today the biggest crater on our planet. Scientists have widely accepted, based on previous research, that the impact structure, known as the Vredefort crater, was formed by an object about 15 kilometers (approximately 9.3 miles) in diameter that was travelling at a velocity of 15 kilometers per second.
But according to new research from the 糖心传媒, the impactor may have been much bigger糖心传媒攁nd would have had devastating consequences across the planet. This research, published in the , provides a more accurate understanding of the large impact and will allow researchers to better simulate impact events on Earth and other planets, both in the past and the future.
糖心传媒淯nderstanding the largest impact structure that we have on Earth is critical,糖心传媒� says 糖心传媒�20, now a PhD student at Johns Hopkins University. Allen is the first author of the paper, based on research she conducted as an undergraduate at Rochester with , an assistant professor of . 糖心传媒淗aving 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.糖心传媒�
Updated simulations suggest 糖心传媒榙evastating糖心传媒� consequences
Over the course of two billion years, the Vredefort crater has eroded. This makes it difficult for scientists to directly estimate the size of the crater at the time of the original impact, and therefore the size and velocity of the impactor that formed the crater.
An object that is 15 kilometers in size and traveling at a velocity of 15 kilometers per second would produce a crater about 172 kilometers in diameter. However, this is much smaller than current estimates for the Vredefort crater. These current estimates are based on new geological evidence and measurements estimating that the structure糖心传媒檚 original diameter would have been between 250 and 280 kilometers (approximately 155 and 174 miles) during the time of the impact.
Allen, Nakajima, and their colleagues conducted simulations to match the updated size of the crater. Their results showed that an impactor would have to be much larger糖心传媒攁bout 20 to 25 kilometers糖心传媒攁nd traveling at a velocity of 15 to 20 kilometers per second to explain a crater 250 kilometers in size.
This means the impactor that formed the Vredefort crater would have been larger than the asteroid that killed off the dinosaurs 66 million years ago, forming the Chicxulub crater. That impact had damaging effects globally, including greenhouse heating, widespread forest fires, acid rain, and destruction of the ozone layer, in addition to causing the Cretaceous-Paleogene extinction event that killed the dinosaurs.
If the Vredefort crater was even larger and the impact more energetic than that which formed the Chicxulub crater, the Vredefort impact may have caused even more catastrophic global consequences.
糖心传媒淯nlike 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 two billion years ago,糖心传媒� Nakajima says. 糖心传媒淗owever, the impact would have affected the global climate potentially more extensively than the Chicxulub impact did.糖心传媒�
Dust and aerosols from the Vredefort impact would have spread across the planet and blocked sunlight, cooling the Earth糖心传媒檚 surface, she says. 糖心传媒淭his could have had a devastating effect on photosynthetic organisms. After the dust and aerosols settled糖心传媒攚hich could have taken anywhere from hours to a decade糖心传媒攇reenhouse gases such as cardon dioxide that were emitted from the impact would have raised the global temperature potentially by several degrees for a long period of time.糖心传媒�
A multi-faceted model of Vredefort crater
The simulations also allowed the researchers to study the material ejected by the impact and the distance the material traveled from the crater. They can use this information to determine the geographic locations of land masses billions of years ago. For instance, previous research determined material from the impactor was ejected to present-day Karelia, Russia. Using their model, Allen, Nakajima, and their colleagues found that, two billion years ago, the distance of the land mass containing Karelia would have been only 2,000 to 2,500 kilometers from the crater in South Africa糖心传媒攎uch closer than the two areas are today.
糖心传媒淚t is incredibly difficult to constrain the location of landmasses long ago,糖心传媒� Allen says. 糖心传媒淭he current best simulations have mapped back about a billion years, and uncertainties grow larger the further back you go. Clarifying evidence such as this ejecta layer mapping may allow researchers to test their models and help complete the view into the past.糖心传媒�
Undergraduate research leads to publication
The idea for this paper arose as part of a final for the course Planetary Interiors (now named Physics of Planetary Interiors), taught by Nakajima, which Allen took as a junior.
Allen says the experience of having undergraduate work result in a peer-reviewed journal article was very rewarding and helped her when applying for graduate school.
糖心传媒淲hen Professor Nakajima approached me and asked if I wanted to work together to turn it into a publishable work, it was really gratifying and validating,糖心传媒� Allen says. 糖心传媒淚 had formulated my own research idea, and it was seen as compelling enough to another scientist that they thought it was worth publishing!糖心传媒�
She adds, 糖心传媒淭his project was way outside of my usual research comfort zone, but I thought it would be a great learning experience and would force me to apply my skills in a new way. It gave me a lot of confidence in my research abilities as I prepared to go to graduate school.糖心传媒�
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