Massive asteroid crash 35 million years ago had no climate impact

Around 35.65 million years ago, two massive asteroids collided with Earth. Despite the scale of these asteroid impacts, a new study by researchers at University College London (UCL) reveals that they did not trigger any lasting changes in Earth’s climate.

This surprising discovery comes from examining isotopes in tiny marine fossils from that era that offer insights into the resilience of Earth’s climate system.

A tale of two craters

These two space rocks, each several miles wide, struck Earth about 25,000 years apart.

One hit the region that is now Chesapeake Bay in the United States, creating a crater 25 to 55 miles (40 to 85 kilometers) in diameter.

The other impacted Siberia, forming the 60-mile-wide (100 kilometers) Popigai crater. These are the fourth and fifth largest asteroid craters known on Earth, respectively. Yet, despite their size, their effect on Earth’s climate appears to have been minimal in the long run.

The study, recently published in the journal Communications Earth & Environment, found no evidence of significant, lasting climate changes in the 150,000 years following the impacts. This contradicts prior theories that linked such collisions with periods of extreme cooling or warming.

Ancient climate after asteroid impacts

The research team inferred ancient climate conditions by analyzing isotopes in tiny fossils from a group of marine organisms known as foraminifera. These single-celled organisms lived both near the surface and on the seafloor of ancient oceans.

“What is remarkable about our results is that there was no real change following the impacts,” noted study co-author Professor Bridget Wade from UCL Earth Sciences.

“We expected the isotopes to shift in one direction or another, indicating warmer or cooler waters, but this did not happen. These large asteroid impacts occurred and, over the long term, our planet seemed to carry on as usual.”

The fossils came from a rock core drilled beneath the Gulf of Mexico by the scientific Deep Sea Drilling Project. The samples ranged in age from 35.5 to 35.9 million years.

The researchers looked at both benthic foraminifera, which lived on the seafloor, and planktonic foraminifera, which floated near the surface. This approach allowed them to form a comprehensive picture of how ocean temperatures responded.

Short-term chaos, long-term stability

The asteroid impacts would have been catastrophic on a human timescale.

“Over a human time scale, these asteroid impacts would be a disaster. They would create a massive shockwave and tsunami, there would be widespread fires, and large amounts of dust would be sent into the air, blocking out sunlight,” noted Professor Wade.

However, the samples they studied were spaced every 11,000 years, which means shorter-term changes over tens or hundreds of years might not be visible in their data.

Indeed, the Chicxulub impact that led to the extinction of the dinosaurs about 66 million years ago caused climate shifts over a much shorter time – less than 25 years, according to modeling studies.

Despite the absence of a long-term impact on Earth’s climate, Professor Wade emphasized the importance of continuing to monitor space and fund asteroid deflection missions.

“We still need to know what is coming and fund missions to prevent future collisions,” she cautioned.

Earth’s resilience to catastrophe

Interestingly, the researchers did see climate changes that were not associated with the asteroid impacts.

Isotope analysis showed warming of about 2 degrees Celsius at the ocean surface and a 1-degree cooling in deep waters, about 100,000 years before the asteroid events. However, around the time of the impacts and afterward, there were no notable changes.

“Given that the Chicxulub impact likely led to a major extinction event, we were curious to investigate whether what appeared as a series of sizeable asteroid impacts during the Eocene also caused long-lasting climate changes,” explained study co-author and MSc Geosciences graduate Natalie Cheng.

“We were surprised to discover that there were no significant climate responses to these impacts.”

The study’s findings highlight Earth’s resilience in the face of these ancient catastrophes.

“It was fascinating to read Earth’s climate history from the chemistry preserved in microfossils. It was especially interesting to work with our selection of foraminifera species and discover beautiful specimens of microspherules along the way,” Cheng added.

Asteroid impacts beyond climate

While this study suggests that Earth’s climate can remain stable even after massive impacts, it also underscores the potential for asteroid impacts to cause significant short-term disruptions.

The two asteroids, which were between two and five miles wide, each created a massive shockwave upon impact.

Evidence also points to three smaller asteroid collisions during the late Eocene epoch, indicating a disturbance in our solar system’s asteroid belt at that time. These smaller impacts add to the mystery of what was happening in space that may have sent so many asteroids our way.

Significance of the study

The study’s funding came from the UK’s Natural Environment Research Council (NERC), reflecting the importance of understanding the role of asteroid collisions in Earth’s geological history.

Despite the lack of a long-term climate impact from these two asteroid impacts, the findings are crucial for building a comprehensive view of Earth’s climate history and the resilience of life on our planet.

Asteroid collisions with Earth remain a real threat. Though these events might not always lead to permanent changes, their destructive potential in the short term cannot be ignored.

The world needs continued investment in asteroid detection and deflection missions to ensure we are well prepared for the day when another giant space rock comes our way.

The study is published in the journal Communications Earth & Environment.

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