Two Giant Asteroids, 25,000 Years Apart, Leave Huge Craters but No Climate Chaos
Around 35.65 million years ago, Earth was hit by not one but two massive asteroids within a span of just 25,000 years. These space rocks—one as wide as Mount Everest is tall—punched enormous craters into the planet: the 60-mile-wide Popigai crater in Siberia and the Chesapeake Bay crater in the United States, measuring between 25 and 55 miles across.
You’d think such colossal collisions would throw Earth’s climate into a tailspin, but according to a study by researchers at University College London, our planet shrugged it off like a champ. Their findings suggest that these massive impacts didn’t cause any lasting climate changes, defying expectations and earlier theories.
How Did Scientists Unlock This Ancient Mystery?
The team analyzed over 1,500 fossils of tiny marine organisms called foraminifera, which are essentially the ocean’s time capsules. These creatures, both surface-dwellers and seafloor residents, recorded ocean temperatures in their shells. The researchers extracted these fossils from a three-meter-long rock core drilled beneath the Gulf of Mexico.
By examining the carbon and oxygen isotopes within the foraminifera, scientists could reconstruct a detailed climate history for the period spanning 35.5 to 35.9 million years ago. What they found was shocking: no significant shifts in climate tied to the asteroid impacts.
A Close Call, but No Long-Term Fallout
While the Chicxulub asteroid 66 million years ago famously triggered a global catastrophe and wiped out the dinosaurs, these late-Eocene impacts were different. Yes, they caused immediate destruction—think towering tsunamis, massive shockwaves, and skies darkened by dust—but their effects were relatively short-lived.
The study’s resolution (sampling every 11,000 years) was too broad to capture short-term changes, but over the long haul—spanning 150,000 years—Earth’s climate appeared unaffected. As Professor Bridget Wade of UCL Earth Sciences put it, “Over a human time scale, these asteroid impacts would be a disaster. But over geological time, the planet carried on as usual.”
Traces of Cosmic Chaos: Glass Droplets and Warming Before the Impacts
Interestingly, the rock samples also contained thousands of microscopic glass droplets called microspherules. These form when asteroid impacts vaporize silica-rich rocks, which cool and solidify as they re-enter the atmosphere.
Even more fascinating? The researchers observed a warming trend of about 2°C in surface waters and a 1°C cooling in deep waters roughly 100,000 years before the impacts. This shift wasn’t linked to the asteroid strikes, suggesting other climatic factors were at play before these cosmic events.
The findings highlight Earth’s incredible resilience but also underscore the need for caution. While these Eocene impacts didn’t cause a global crisis, every asteroid is different. The Chicxulub event shows how devastating one collision can be, depending on its size, speed, and composition.
As co-author Natalie Cheng remarked, “It’s crucial to keep studying Earth’s climate history through fossils. It’s like reading a diary written in stone.” With modern advancements in asteroid detection and planetary defense strategies, we’re better equipped than ever to avoid becoming the next chapter in Earth’s collision story.
