108
What would happen if a 500-meter asteroid hit Earth? Scientists from the Center for Climate Physics at the Institute for Basic Sciences (IBS) have simulated the consequences of such an impact, revealing a dramatic plunge into a “shock winter”: temperatures would drop by 4°C, precipitation would decrease by 15%, and ozone depletion would reach 32%.
The result? A global food crisis due to a 30% reduction in terrestrial photosynthesis. But the ocean tells a different story—plankton, fueled by iron-rich asteroid dust, can actively reproduce, causing massive algal blooms. This unexpected marine boom could be a salvation for the biosphere. Could similar asteroid impacts have influenced human evolution? Future research aims to study how our ancestors survived such cataclysms.
Asteroid impact: an event that changes climate and life
A recent climate modeling study published on February 5 in Science Advances, conducted by researchers at IBS at Pusan National University (South Korea), shows how Earth's climate and ecosystems might respond to a collision with a medium-sized asteroid (~500 meters). The solar system contains many near-Earth objects, most of which pose no threat. However, some of them have a small but significant chance of colliding with Earth. One such object is the asteroid Bennu, which is about 500 meters in diameter. According to a 2021 study (Farnocchia et al.), the probability of it colliding with Earth in September 2182 is 1 in 2700 — about the same as flipping a coin 11 times in a row and getting the same result.
Modeling the consequences of an asteroid impact
To determine the potential consequences of an asteroid impact on climate, terrestrial plants and ocean plankton, the IBS researchers used a modern climate model. The impact of the impact is represented as a massive ejection of hundreds of millions of tons of dust into the upper atmosphere. Unlike previous studies, this work also takes into account the response of terrestrial and marine ecosystems, as well as complex chemical processes in the atmosphere.
Supercomputer predictions: Earth is plunging into darkness and cold
Using a supercomputer Aleph, researchers have simulated several scenarios of a collision with an asteroid like Bennu. According to these simulations, massive dust emissions (100–400 million tons) would lead to serious climate shocks, changes in atmospheric composition, and global photosynthesis within 3–4 years of impact. In the most intense scenario, the solar eclipse by dust would cause a global temperature drop of 4°C, a 15% reduction in average precipitation, and a 32% depletion of the ozone layer. However, in some regions, these effects would be even more severe.
"Sudden" winter storm "will create unfavorable conditions for plant growth, leading to an initial 20–30% reduction in photosynthesis in both terrestrial and marine ecosystems. This is likely to cause massive disruptions to global food security," said Dr. Lan Dai, lead author of the study.
The unexpected recovery of the ocean
Analyzing ocean modeling data, the researchers found something unexpected: plankton growth followed a different pattern. Instead of a sharp decline like on land, plankton in the sea rebounded within six months and even increased to levels not seen under normal climate conditions.
"We were able to trace this unexpected response to the concentration of iron in the dust," says Professor Axel Timmermann, Director of ICCP and co-author of the study.
Iron is a key element for algae growth, but in some regions, such as the Southern Ocean and the eastern tropical Pacific, its natural levels are very low. Depending on the iron content of the asteroid and the terrestrial material that entered the stratosphere after the impact, these nutrient-poor regions could suddenly receive a massive influx of bioavailable iron, triggering unprecedented algal blooms. According to computer simulations, the greatest increase in marine productivity will occur among diatoms, which in turn will attract large numbers of zooplankton—small predators that feed on these algae.
Can plankton blooms save the ecosystem?
“Simulated excessive blooms of phytoplankton and zooplankton may prove to be a boon to the biosphere and partially compensate for the food crisis caused by declining terrestrial productivity,” adds Dr. Lan Dai.
"On average, medium-sized asteroids collide with Earth every 100-200 years. This means that our early ancestors could have experienced such catastrophes, which may have influenced the evolution of humanity and even our genetic code," says Professor Timmermann.
Looking to the past to understand the future
This research opens new perspectives in studying the climatic and ecological consequences of near-Earth asteroid impacts. As a next step, the ICCP team plans to investigate how early humans might have adapted to such disasters, using agent-based computer models that simulate the behavior of individuals, their life cycles, and their foraging.
