Asteroid that formed Vredefort crater bigger than previously believed
An impactor—most likely an asteroid—hurtled toward Earth about two billion years ago, crashing into the planet near present-day Johannesburg, South Africa. The impactor formed Vredefort crater, what is today the biggest crater on our planet. Using updated simulation data, University of Rochester researchers discovered the impactor that formed Vredefort crater was much larger than previously believed. Credit: NASA Earth Observatory image by Lauren Dauphin / University of Rochester illustration by Julia Joshpe

The planet was hit by an impactor about 2 billion years ago. The largest crater on our planet was formed by the impactor. The Vredefort crater was formed by an object that traveled at a speed of 15 kilometers per second.

According to new research from the University of Rochester, the impactor may have been much bigger than previously thought. The research published in the Journal of Geophysical Research: Planets provides a more accurate understanding of the large impact and will allow researchers to better simulations of impact events on Earth and other planets.

Natalie Allen says that understanding the largest impact structure is important. Allen is the first author of the paper, based on research she did as an undergrad at Rochester. We can better understand impacts on Earth and beyond if we have access to the information provided by the Vredefort crater.

Simulations suggest dire consequences.

The Vredefort crater has eroded over two billion years. Scientists can't directly estimate the size of the crater at the time of the original impact because of this.

A crater of 172 kilometers in diameter would be created by an object that is 15 kilometers in size and travelling at a speed of 15 kilometers per second. Current estimates for the Vredefort crater are larger than this one. The structure's original diameter is thought to have been between 250 and 280 kilometers during the time of the impact.

Simulations were conducted to match the size of the crater. A crater of 250 kilometers in size would have to be larger than 20 to 25 kilometers and travel at a speed of 15 to 20 kilometers per second, according to their results.

The impactor that formed the Vredefort crater was larger than the one that killed off the dinosaurs. Acid rain, greenhouse heating, forest fires, and destruction of the ozone layer were all caused by that impact.

The Vredefort impact may have caused more catastrophic global consequences if it was larger and more energetic.

The Vredefort impact did not leave a record of mass extinction or forest fires because there were only single-cell life forms. The impact would have had a bigger impact on the global climate.

Dust and aerosols from the Vredefort impact would have created a cooling effect on the Earth. It could have been a disaster for the organisms. Greenhouse gases such as carbon dioxide that were emitted from the impact would have raised the global temperature for a long period of time.

There is a model of the crater.

Researchers were able to study the material ejected by the impact and the distance it traveled from the crater. This information can be used to figure out the location of land mass billions of years ago. Material from the impactor was thrown to Russia. The model used by Allen, Nakajima, and their colleagues shows that the land mass containing Karelia is much closer to the crater in South Africa than it is today.

Allen says it's difficult to locate landmasses long ago. The current best simulations have been around for a billion years. Researchers may be able to complete the view into the past by clarifying evidence such as this.

The results of undergraduate research are published.

As a junior, Allen took a final for the course Planetary Interiors, taught by Nakajima, which led to the creation of this paper.

When applying for graduate school, Allen says the experience of having undergrad work result in a peer-reviewed journal article helped her.

Allen says that when Professor Nakajima asked if he wanted to work together to turn it into a publication, it was gratifying. I formulated my own research idea and it was seen as compelling enough to be published.

She says that she thought the project would be a great learning experience and would force her to apply her skills in a different way. As I prepared to go to graduate school, it gave me a lot of confidence.

More information: Natalie H. Allen et al, A Revision of the Formation Conditions of the Vredefort Crater, Journal of Geophysical Research: Planets (2022). DOI: 10.1029/2022JE007186