WASHINGTON – The near-Earth asteroid Bennu, which approaches our planet every six years, has a small but concerning chance of colliding with Earth in September 2182. Scientists estimate the probability of impact at 1 in 2,700, but new research suggests that if such an event were to occur, the consequences would be devastating.
Using advanced computer simulations, researchers examined the potential effects of a Bennu-sized asteroid—measuring about 500 meters (0.3 miles) in diameter—striking Earth. Beyond the immediate destruction from the impact itself, the study found that such a collision could inject 100-400 million tons of dust into the atmosphere, triggering widespread climate disruptions.
The dust would block sunlight, leading to an abrupt global “impact winter” with reduced temperatures, decreased precipitation, and diminished plant growth, according to Lan Dai, a postdoctoral research fellow at the IBS Center for Climate Physics (ICCP) at Pusan National University in South Korea. The study, published in Science Advances, suggests that in a worst-case scenario:
- Global average temperatures could drop by 4°C (7°F)
- Rainfall could decline by 15%
- Plant photosynthesis could be reduced by 20-30%
- The ozone layer could be depleted by 32%, increasing UV radiation exposure
On land, the impact would cause massive shockwaves, earthquakes, wildfires, and thermal radiation, devastating the surrounding area. The asteroid would leave a crater, ejecting debris high into the atmosphere, further worsening the climate crisis.
While land-based ecosystems would struggle, ocean life could see a quicker rebound. The study suggests that plankton populations might recover within six months, thanks to iron-rich asteroid dust stimulating diatom blooms. However, the stratosphere—Earth’s second atmospheric layer—would suffer severe ozone depletion, increasing risks to both ecosystems and human health.
Bennu is classified as a “rubble pile” asteroid, a loosely bound collection of rock and dust that formed around 4.5 billion years ago. NASA’s OSIRIS-REx mission collected samples from Bennu in 2020, revealing organic molecules that support the theory that asteroids may have contributed to life on Earth.
History has shown that asteroid impacts can be catastrophic. A 10-15 km (6-9 mile) asteroid impact near Mexico’s Yucatán Peninsula 66 million years ago is believed to have wiped out 75% of Earth’s species, including the dinosaurs.
To prevent such a disaster, NASA successfully tested planetary defense strategies in 2022, altering the trajectory of the asteroid Dimorphos using the DART spacecraft. The experiment proved that future asteroid deflection missions could be viable.
While the probability of Bennu striking Earth remains just 0.037%, study co-author Axel Timmermann emphasized the importance of preparedness.
“Even though the likelihood is small, the impact would likely result in massive food insecurity and climate disruptions, similar to the largest volcanic eruptions of the past 100,000 years,” Timmermann stated. “It’s crucial to assess and prepare for this risk.”
With planetary defense efforts advancing, scientists continue to monitor Bennu and other near-Earth objects to ensure that if a future collision threat emerges, humanity will be ready to respond.