In a recent study, scientists at the IBS Center for Climate Physics (ICCP) at Pusan National University in South Korea simulated the aftermath of a Bennu-type, medium-sized asteroid collision with Earth, shedding light on the potential climatic and ecological consequences.
The findings, published in Science Advances, reveal that such an impact could dramatically cool the planet, leading to widespread devastation of plant life and disruptions in global food chains.
The results not only offer a cautionary tale for Earth’s future but also a window into the planet’s ancient past.
“On average, medium-sized asteroids collide with Earth about every 100–200 thousand years,” Director of the ICCP and co-author of the study, Dr. Axel Timmermann, said in a press release. “This means that our early human ancestors may have experienced some of these planet-shifting events before with potential impacts on human evolution and even our own genetic makeup.”
The study is based on the latest orbital projections of asteroid 101955 Bennu, a 500-meter-wide near-Earth object (NEO) that NASA and other space agencies have closely tracked.
Bennu follows an orbit around the Sun, bringing it close to Earth approximately every six years. While the chances of a collision are extremely low, the latest calculations suggest that Bennu has a minuscule but nonzero probability of impacting Earth sometime between 2178 and 2290. The highest likelihood occurs in the year 2182 when the asteroid’s chance of collision is estimated at just 0.037%.
Despite these long odds, Bennu is considered one of the most potentially hazardous asteroids, ranking third on NASA’s JPL Sentry System, which assesses the cumulative risk of a future asteroid impact.
While the chances of Bennu striking Earth are slim, the impact would release an immense amount of energy, equivalent to several thousand nuclear bombs. Such a collision could create a crater nearly six miles wide and half a mile deep, causing widespread devastation. This potential for catastrophic consequences makes Bennu a key focus of planetary defense research and climate impact modeling.
Using advanced climate models, researchers simulated the effects of a Bennu-like asteroid impact on Earth’s atmosphere and biosphere. The researchers could reconstruct the sequence of events following such a colossal collision by inputting variables such as the size of the asteroid, impact angle, and the composition of vaporized materials.
The simulations indicated that the immediate aftermath would involve massive amounts of debris and aerosols being ejected into the atmosphere. These particles would block sunlight, dramatically dropping global temperatures and causing a hypothesized phenomenon known as “impact winter.”
The simulations indicated that mean temperatures could plummet by as much as nearly 40°F globally, with the cooling effect persisting for several years.
The abrupt temperature decline would have profound implications for plant life. Reduced solar radiation would severely hamper photosynthesis, the process by which plants convert sunlight into energy.
Researchers estimated that the net rate at which plants produce biomass would dramatically decrease, leading to a global food crisis. “The abrupt ‘impact winter’ would provide unfavorable climate conditions for plants to grow, leading to an initial 20–30% reduction of photosynthesis in terrestrial and marine ecosystems,” lead author of the study and postdoctoral research fellow at the ICCP, Dr. Lan Dai, explained. “This would likely cause massive disruptions in global food security.”
An impact with a Bennu-like asteroid would set off a chain reaction of environmental disruptions, causing severe consequences for life on Earth. With a significant reduction in plant biomass, herbivorous species would face food shortages, leading to population declines. This, in turn, would impact carnivorous species, creating a ripple effect through the food chain.
The simulations suggested that these ecological disruptions could persist for decades, underscoring the long-term consequences of such an impact.
Surprisingly, while terrestrial ecosystems would struggle for years to recover, the oceanic response to an asteroid impact appears to follow a different trajectory.
According to the study’s simulations, phytoplankton—tiny marine organisms that form the foundation of the oceanic food web—would initially experience a sharp decline due to reduced sunlight. However, unlike land-based vegetation, which would take years to rebound, plankton populations in the ocean would recover within just six months.
Even more unexpectedly, their numbers would eventually surge to levels higher than those seen under normal climate conditions. Researchers say this rebound is likely driven by the influx of iron-rich dust from the impact, which acts as a nutrient boost in iron-limited regions of the ocean, fueling rapid phytoplankton growth.
This short-term marine productivity spike could temporarily offset some of the disruptions in the global food chain, potentially compensating for the widespread collapse of terrestrial agriculture and ecosystems.
“Depending on the iron content of the asteroid and of the terrestrial material that is blasted into the stratosphere, the otherwise nutrient-depleted regions can become nutrient-enriched with bioavailable iron, which in turn triggers unprecedented algae blooms,” Dr. Timmermann said. “The simulated excessive phytoplankton and zooplankton blooms might be a blessing for the biosphere and may help alleviate emerging food insecurity related to the longer-lasting reduction in terrestrial productivity.”
The study also delved into the role of specific atmospheric components in driving the observed climatic changes. Sulfur aerosols, released from vaporized rocks at the impact site, were identified as a key factor in the prolonged cooling.
These particles have a high albedo, meaning they effectively reflect sunlight back into space, thereby reducing the amount of solar energy reaching Earth’s surface. The simulations indicated that sulfur-induced cooling could last longer than previously estimated, with recovery times extending over several years.
In addition to sulfur aerosols, the study examined the impact of soot and dust generated by widespread wildfires ignited by the initial heat of the impact. These microscopic particles released in the air would further reduce sunlight, compounding the cooling effect. The combined presence of sulfur aerosols, soot, and dust creates a complex interplay of radiative forces that drive the climatic response observed in the simulations.
The findings draw comparisons to the Cretaceous-Paleogene extinction event 66 million years ago, which is widely believed to have been triggered by the impact of an asteroid roughly three times the size of Bennu. That cataclysmic collision is estimated to have wiped out nearly 75% of Earth’s species, including all non-avian dinosaurs.
This recent research provides a more detailed understanding of the mechanisms that could drive such mass extinctions, emphasizing the role of climatic changes induced by atmospheric particles.
In today’s context, the study is a stark reminder of Earth’s vulnerability to extraterrestrial threats. While large asteroid impacts are rare, their potential consequences are catastrophic. The research underscores the importance of continued investment in planetary defense initiatives to detect and mitigate potential asteroid threats.
Moreover, the findings highlight the interconnectedness of Earth’s fragile ecosystems and the far-reaching consequences that can result from disruptions to this delicate balance.
“Medium-sized asteroid impacts, similar to other sun-blocking catastrophes, including nuclear winter and large volcanic eruptions, would cause abrupt climate cooling that leads to severe environmental consequences,” researchers conclude. “The abrupt cooling and ecosystem collapses caused by asteroid collisions would severely reduce the habitat suitability for humans, wildlife, and terrestrial ecosystems.”
Tim McMillan is a retired law enforcement executive, investigative reporter and co-founder of The Debrief. His writing typically focuses on defense, national security, the Intelligence Community and topics related to psychology. You can follow Tim on Twitter: @LtTimMcMillan. Tim can be reached by email: tim@thedebrief.org or through encrypted email: LtTimMcMillan@protonmail.com