Near-Earth objects populate the solar system, with some posing a measurable risk of collision with our planet. Among them, asteroid Bennu, measuring approximately 500 meters in diameter, has an estimated 1-in-2700 probability of impacting Earth in September 2182, according to research by Farnocchia et al. (2021). To better understand the potential ramifications of such an event, ICCP researchers utilized state-of-the-art climate models to simulate the atmospheric and ecological disruptions that could follow a collision of this magnitude.

The simulated impact scenario assumes the ejection of several hundred million tons of dust into the upper atmosphere, significantly affecting global climate patterns. Unlike prior studies, this research integrates terrestrial and marine ecosystems along with detailed atmospheric chemistry to provide a comprehensive assessment of the potential changes.

Utilizing the IBS supercomputer Aleph, the team modeled multiple dust injection scenarios, ranging from 100 to 400 million tons. Their findings indicate severe climate disruptions, including a dramatic reduction in sunlight reaching Earth's surface, resulting in a temperature drop of up to 4C, a 15% decline in global mean precipitation, and approximately 32% ozone depletion. These effects would be most pronounced in specific regions, exacerbating localized environmental consequences.

"The abrupt impact winter would create challenging conditions for plant growth, initially reducing photosynthesis in terrestrial and marine ecosystems by 20-30%," explained Dr. Lan DAI, postdoctoral research fellow at ICCP and lead author of the study. "Such disruptions could have significant repercussions for global food security."

Interestingly, oceanic ecosystems exhibited a divergent response. While terrestrial photosynthesis suffered a prolonged decline lasting up to two years, plankton populations in the ocean rebounded within six months, even surpassing pre-impact levels. This phenomenon was traced to an increased presence of iron-rich dust, which fertilized the ocean and stimulated unprecedented algal blooms in regions where iron is typically scarce, such as the Southern Ocean and the eastern tropical Pacific.

"Our simulations show that iron from the asteroid impact and terrestrial material lifted into the stratosphere could significantly enrich nutrient-depleted regions, triggering widespread phytoplankton growth," noted Prof. Axel TIMMERMANN, Director of ICCP and co-author of the study. The model projections suggest that diatoms, a type of silicate-rich algae, would dominate these post-impact blooms, attracting large populations of zooplankton that feed on them.

Dr. DAI added, "The surge in marine productivity could offer some ecological benefits, potentially offsetting food shortages caused by reduced terrestrial productivity."

Historically, Earth experiences medium-sized asteroid impacts approximately every 100,000 to 200,000 years. Prof. Timmermann highlighted the potential evolutionary significance of such events, suggesting that early human populations may have encountered similar planetary disruptions, influencing both genetic development and survival strategies.

The ICCP team intends to extend their research by employing agent-based modeling techniques to simulate human behavioral responses to such catastrophic events, further exploring the potential implications for human evolution and adaptation.

Research Report:Climatic and ecological responses to Bennu-type asteroid collisions

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