Meteorite 200 times larger than the dinosaur-killing asteroid hit Earth 3.3 billion years ago. But it helped life to flourish

The most striking illustration of the destructive power of space rocks on Earth is the asteroid that wiped out the dinosaurs and about three-quarters of all plant and animal species around 66 million years ago. 

However, scientists have recently discovered evidence of an even older and larger meteorite that struck Earth — one that may have actually helped life flourish rather than destroying it. This impact occurred around 3.3 billion years ago, during the solar system’s early years, when asteroid collisions were far more frequent. 

This meteorite, designated as S2, is roughly 200 times larger than the Chicxulub responsible for the dinosaurs’ extinction. When S2 hit Earth, off the coast of Cape Cod, only single-celled organisms were present. The impact boiled the oceans, drove global darkness and triggered tsunamis that shredded coastal seafloors. 

However, the devastation may have spurred a significant increase in bacterial and archaeal populations. 

Nadja Drabon, a Harvard geologist, and her team discovered evidence of this ancient impact in South Africa’s Barberton Greenstone belt. They meticulously collected rock samples, analyzed their chemical compositions, and studied the distribution of various carbon isotopes, allowing them to reconstruct the events surrounding the S2 impact. 

“We often view impact events as catastrophic for life,” said Drabon, the team leader. “This study suggests that such impacts might have actually facilitated life’s expansion, especially in its early stages.”  

Their research was published on October 21 in the ‘Proceedings of the National Academy of Sciences’. 

When S2 collided with Earth, it would have generated a massive tsunami that churned the ocean floor and flooded coastal areas with debris. The extreme heat from the impact would have boiled off the upper layers of the ocean and heated the atmosphere. 

The impact would have launched debris into the atmosphere, creating a thick dust cloud that blocked sunlight, hindering photosynthesis for many simple organisms. However, certain bacteria managed to survive and recover rapidly. The researchers believe that unicellular organisms that consumed iron and phosphorus thrived in the aftermath of this catastrophic event. 

The spikes in populations of certain unicellular strains were likely due to iron being dredged from the deep ocean and delivered to shallower waters by the tsunami. An influx of phosphorus would have occurred as land eroded and additional phosphorus was introduced by the impact itself, the researchers said. 

The researchers theorize that iron-consuming bacteria initially flourished after S2’s impact, albeit briefly. This shift toward iron-metabolising bacteria adds to our understanding of life’s early evolution on Earth. 

This discovery marks the eighth asteroid impact identified in the area studied by Drabon and her team. Their findings were made possible through intensive fieldwork, scouring mountain passes for sedimentary evidence of ancient impacts that have been preserved over time. 

The team plans to continue exploring the region for more signs of asteroid strikes, tsunamis, and other cataclysmic events that could shed light on Earth’s history.