How a small asteroid impact would change life on modern-day Earth

Throughout history, Earth has faced cataclysmic events that reshaped its climate and ecosystems. Some of these events were triggered by asteroid impacts, leaving long-lasting effects on both land and sea.

Scientists continue to study these possibilities, not just to understand past extinctions but to prepare for potential future threats.

A recent study by researchers from the IBS Center for Climate Physics (ICCP) at Pusan National University in South Korea explores what would happen if a medium-sized asteroid struck Earth.

Using advanced climate models, the research team simulated how such an impact could disrupt the atmosphere, weather patterns, and even global food security.

The findings reveal a world drastically altered, with some life struggling to survive while other forms unexpectedly thrive.

Risk of an asteroid collision

Earth is surrounded by countless objects with relatively close orbits. Most pose no immediate threat, but some have collision probabilities that cannot be ignored.

One of the more notable objects is the asteroid Bennu, which measures about 500 meters in diameter. According to recent studies, there is a 1-in-2700 chance that Bennu could collide with Earth in September 2182.

To put that probability into perspective, it is similar to flipping a coin 11 times and getting the same outcome every time.

While such a scenario remains unlikely, the potential consequences are severe enough to warrant scientific investigation.

If an asteroid of this size were to strike, the damage would go far beyond the initial impact zone, triggering worldwide disruptions that could last for years.

Simulating an asteroid impact

To understand the potential consequences, researchers at ICCP created an advanced climate model to simulate a medium-sized asteroid collision.

Their model assumed that an impact would release several hundred million tons of dust into the upper atmosphere. This dust would block sunlight, triggering a global cooling event similar to what happened after massive volcanic eruptions in Earth’s past.

Unlike previous studies, which focused mainly on atmospheric and temperature changes, this research also examined the effects on terrestrial and marine ecosystems.

The team wanted to determine how plant life, both on land and in the ocean, would respond to the sudden climate shift.

Using the IBS supercomputer Aleph, the researchers ran multiple scenarios, varying the amount of dust injected into the atmosphere.

The results showed widespread disruption to climate, atmospheric chemistry, and global photosynthesis for at least three to four years after the impact.

Climate changes due to asteroid collision

The most extreme scenario revealed that solar dimming caused by dust would lead to a global surface cooling of up to 4°C.

This drop in temperature would have a severe impact on agriculture, making it harder for crops to grow in many parts of the world.

Rainfall would also decrease by around 15%, further worsening food production. In addition, the study predicted ozone depletion of about 32%, exposing life to harmful ultraviolet radiation.

While these changes would affect the entire planet, some regions would suffer more than others. Areas already prone to drought could experience even harsher conditions, while colder regions might see longer, more intense winters.

The disruptions would make it difficult for many species, including humans, to adapt quickly.

Impact on land and ocean ecosystems

Dr. Lan DAI, a postdoctoral research fellow at ICCP and lead author of the study, explained how these changes would affect ecosystems across the globe.

“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. This would likely cause massive disruptions in global food security,” said Dr. Lan DAI.

While land plants would struggle with the sudden drop in temperature and reduced sunlight, the researchers found something surprising when they analyzed ocean plankton.

Unlike their land-based counterparts, plankton displayed an entirely different response to the impact.

Surprising recovery in the ocean

The computer models showed that while photosynthesis on land declined sharply, ocean plankton rebounded quickly.

Within six months, plankton levels returned to normal, and in some cases, they even surpassed pre-impact levels.

This unexpected recovery was linked to the composition of the asteroid dust and its climate impact.

“We were able to track this unexpected response to the iron concentration in the dust,” said Professor Axel Timmermann, Director of the ICCP and co-author of the study.

Iron is a critical nutrient for algae, and in some parts of the ocean, natural iron levels are extremely low. When the asteroid struck, it released iron-rich dust into the atmosphere, which eventually settled into the ocean.

This sudden influx of iron created ideal conditions for algae growth, particularly in nutrient-depleted regions like the Southern Ocean and the eastern tropical Pacific. The result was an explosion of marine productivity, with algae blooms spreading across large ocean areas.

Boom in marine life

The study found that silicate-rich algae, known as diatoms, benefited the most from the increased iron levels.

These microscopic organisms form the base of the marine food chain, meaning their growth would attract higher levels of zooplankton, which feed on them. This process set off a chain reaction, boosting marine life at multiple levels.

“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,” noted Dr. Lan DAI.

While terrestrial ecosystems would struggle for years after an asteroid impact, the ocean might become a refuge for certain species. This unexpected benefit could help balance some of the food shortages caused by declining crop yields on land.

Lessons from past asteroid strikes

Medium-sized asteroids have collided with Earth approximately every 100,000 to 200,000 years. These events have left permanent marks on the planet’s geological and biological history.

Scientists believe that some of these impacts may have shaped human evolution by forcing early human populations to adapt to harsh environmental conditions.

“On average, medium-sized asteroids collide with Earth about every 100-200 thousand years. 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,” said Professor Timmermann.

Studying these past events can help scientists understand how humanity might respond to a future impact. If a medium-sized asteroid were to strike again, modern technology and global cooperation could play a key role in minimizing its effects.

Asteroid-driven climate shifts of the past

The ICCP researchers plan to expand their study by simulating how early human populations might have responded to asteroid-driven climate shifts.

Using agent-based computer models, they aim to recreate the survival strategies of ancient humans as they faced drastic environmental changes.

Understanding past events is crucial, but preparing for the future is just as important. While the chances of an asteroid collision remain low, having scientific models in place can help policymakers and researchers develop strategies to mitigate potential risks.

From planetary defense initiatives to climate adaptation plans, the knowledge gained from these studies could one day prove vital for protecting life on Earth.

The study is published in the journal Science Advances.

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