The Earth has experienced several cataclysmic asteroid impacts over its long geological history, with notable events around 35.65 million years ago. Despite the dramatic nature of such collisions, researchers at University College London have uncovered surprising findings: these massive impacts did not lead to any significant long-term changes in Earth’s climate.
Two asteroids struck at approximately 25,000-year intervals, leaving behind the Popigai crater, which measures about 60 miles (100 km) across, located in Siberia, Russia, and the Chesapeake Bay impact site, about 25-55 miles (40-85 km) wide, found on the eastern coast of the United States. An extensive analysis conducted by the research team aimed to examine climate conditions prior to and following these celestial hits, with findings now published in Communications Earth & Environment.
The cornerstone of this study relied on isotopic analysis of ancient marine fossils, particularly from tiny organisms known as foraminifera. These little shelled creatures provide insights through their fossilized remains, which hold clues to past ocean temperatures. Professor Bridget Wade from UCL Earth Sciences, one of the co-authors, noted, “What is remarkable about our results is there was no real change following the impacts. We expected the isotopes to shift one way or another, indicating warmer or cooler waters, but they remained stable.”
These findings are particularly intriguing. The two significant impacts didn't appear to cause the expected climate shifts over the following 150,000 years. Instead, the planet seemed to move on as if nothing had happened. “We still need to know what is coming and fund missions to prevent future collisions,” emphasized Wade.
While the study provides considerable evidence against long-term climatic upheaval due to these asteroid events, it does not rule out the potential for immediate catastrophes. Wade mentioned the notable destruction caused by such impacts, like shockwaves, tsunamis, and significant amounts of dust—elements capable of blocking sunlight and wreaking havoc on surface conditions. “Over a human time scale, these asteroid impacts would be disasters,” she added.
The researchers examined fossils from 1,500 foraminifera specimens drawn from ocean floor cores, drilled during the Deep Sea Drilling Project in the Gulf of Mexico. Their research also pointed to other potential asteroid encounters during the late Eocene epoch, which may indicate disturbances within our solar system’s asteroid belt.
Previously conducted studies connected the Eocene impacts with both cooling and warming periods, but those investigations lacked high-resolution data, making much of the earlier analyses inconclusive. Wade's team, with finer sampling intervals every 11,000 years and broader data scopes, presented a more accurate representation of how the oceans responded to the impacts.
Interestingly, the research unveiled signs of warming and cooling about 100,000 years prior to the two asteroid impacts, with surface water temperatures showing about 2 degrees Celsius of warming and deep water temperatures cooling by about 1 degree Celsius. Yet no significant shifts were detected during or after the impacts themselves.
Adding to the depth of their findings, the researchers found thousands of tiny glass droplets, formed from silica-containing rocks, embedded within the core samples. These microspherules originated from vaporized rock materials following the impacts, offering a tangible record of the catastrophic events.
Another co-author, Natalie Cheng, shared her surprise at the outcomes, especially considering the historical precedents like the Chicxulub impact, which is believed to have been responsible for the mass extinction of the dinosaurs. “We were curious to investigate whether what appeared as significant impacts during the Eocene also caused climate changes. We were surprised to discover there were no significant climate responses to these impacts,” Cheng said.
Cheng also expressed her fascination with the findings, stating, “It was intriguing to read the history of Earth’s climate through the chemistry preserved in microfossils. Working with foraminifera species and discovering microspherules along the way was incredibly rewarding.”
This research highlights the importance of maintaining vigilance against future asteroid threats, as the findings indicate, even if past impacts did not significantly change the course of climate history, the immediate effects would have been catastrophic at the time. Wade reiterated the need to prepare for such events as part of our scientific agenda moving forward.
The intriguing aspects of climate change and asteroid impacts offer not just lessons from the past but also cautionary tales for the future, reminding humanity of the potential consequences of celestial encounters. The results of this research are pivotal, challenging existing perceptions about the long-term climate effects of big impacts, as the history of our planet continues to be unraveled through scientific inquiry.