Asteroid that formed Vredefort crater bigger than previously believed

An impactor hurtled toward Earth around two billion years ago, striking into the globe not far from where Johannesburg, South Africa is now. The largest crater on Earth was created by the impactor, which was most likely an asteroid. Based on earlier studies, it is largely acknowledged by scientists that the Vredefort crater was created by an object with a diameter of around 15 kilometers (about 9.3 miles) and a speed of 15 kilometers per second.

However, recent study from the University of Rochester suggests that the impactor may have been far larger and would have had catastrophic effects on the entire planet. This study, which was published in the Journal of Geophysical Research, improves our knowledge of the massive impact and paves the way for more realistic simulations of impact events that have occurred on Earth and other planets in the past and will occur in the future.

Understanding the largest effect structure humans have on Earth is crucial, according to Natalie Allen, a 2020 graduate who is now enrolled in the John Hopkins University PhD program. The study's primary author, Allen, did research with assistant professor of Earth and environmental sciences Miki Nakajima while an undergraduate at Rochester. Allen is the author of the report. The opportunity to test our model and our comprehension of the geologic data presented by a structure like the Vredefort crater is excellent since it will help us comprehend impacts on Earth and other planets.

The Vredefort crater has eroded over a two billion year period. The size of the crater at the moment of the initial impact and, consequently, the size and velocity of the impactor that created the crater, are therefore difficult for scientists to properly assess.

A crater measuring 172 kilometers in diameter would be created by an object that is 15 kilometers in size and moving at a speed of 15 kilometers per second. This is far less than the Vredefort crater's estimated size, though. The structure's initial diameter, which is now estimated to have ranged between 250 and 280 kilometers (about 155 and 174 miles) at the time of the impact, is based on new geological data and observations.

Simulations were run by Allen, Nakajima, and their colleagues to match the modified crater size. According to their findings, an impactor would need to be substantially larger, measuring 20 to 25 kilometers, and move at a speed of 15 to 20 kilometers per second in order to account for a crater 250 kilometers in diameter.

This indicates that the asteroid that destroyed the dinosaurs 66 million years ago and left the Chicxulub crater would have been smaller than the impactor that created the Vredefort crater. In addition to triggering the Cretaceous-Paleogene extinction catastrophe that wiped off the dinosaurs, this impact had negative impacts on the entire planet, including greenhouse warming, extensive forest fires, acid rain, and ozone layer loss.

The Vredefort impact may have had even more disastrous worldwide repercussions if the crater was considerably bigger and the energy of the impact greater than that which created the Chicxulub crater.

Given that there were only single-cell lifeforms and no trees two billion years ago, the Vredefort impact did not leave a record of mass extinction or forest fires, in contrast to the Chicxulub impact, claims Nakajima. However, the impact could have had a more significant impact on the world's climate than the Chicxulub impact.

According to her, the Vredefort impact would have caused a global spread of dust and aerosols that would have obstructed sunlight and cooled the Earth's surface. "For species that use sunlight for photosynthesis, this might have been disastrous. The greenhouse gases, such as cardon dioxide, released from the impact would have boosted the world temperature for a very long time, maybe by several degrees, when the dust and aerosols settled, which might take anywhere from hours to a decade."

Researchers were also able to examine the material expelled by the impact and the distance it traveled from the crater thanks to the simulations. They can use this knowledge to pinpoint where specific land masses were geographically billions of years ago. For instance, earlier studies found that the impactor's debris was propelled toward modern-day Karelia, Russia. Using their model, Allen, Nakajima, and their colleagues discovered that the land mass comprising Karelia would have been significantly closer to the crater in South Africa two billion years ago, at a distance of only 2,000 to 2,500 kilometers.

Allen asserts that it is extremely challenging to pinpoint the position of landmasses from the distant past. "The greatest simulations available right now go back approximately a billion years, and the uncertainties increase as you go back more. It may be possible for researchers to test their ideas and further the understanding of the past by elucidating evidence like this ejecta layer mapping."

The inspiration for this essay came from a final exam for Allen's junior-level Nakajima course Planetary Interiors (now called Physics of Planetary Interiors).

Allen claims that having undergraduate research published in a peer-reviewed journal was a very fulfilling experience that aided her in her graduate school applications.

Allen explains, "It was incredibly exciting and affirming when Professor Nakajima reached me and asked if I wanted to work together to develop it into a publishable piece. "I had developed my own research proposal, and another scientist found it intriguing enough to think it was worth publishing!"

She says, "Even though this project was much outside of my normal research comfort zone, I figured it would be a terrific learning opportunity and force me to use my skills in new ways. It greatly increased my confidence in my capacity for research as I got ready to go graduate school."

University of Rochester