The asteroid Bennu has been at the centre of scientific discussions recently, especially after researchers analysed surface samples collected by NASA’s OSIRIS-REx mission. While much of the excitement has revolved around what the space rock can reveal about the origins of life, a new study has introduced a far more unsettling possibility—Bennu could eventually collide with Earth.
Although the chances are slim, scientists estimate that Bennu has a 1-in-2,700 chance of striking our planet. If such an event were to occur, it wouldn’t happen until the year 2182, meaning humanity has at least 157 years to prepare.
While considerably smaller than the asteroid that caused the mass extinction of the dinosaurs 66 million years ago, Bennu still poses a significant threat.
According to the study, published by researchers part of the IBS Centre for Climate Physics, a direct impact would release an estimated 400 million tons of dust, aerosols, and debris into the atmosphere. This would block sunlight, potentially cooling Earth’s surface temperature by 4°C (7.2°F), which could trigger a global winter.
Reduced sunlight would devastate plant life, disrupting food chains and affecting both terrestrial and marine ecosystems. Rainfall levels could drop by 15%, further exacerbating environmental instability.
Asteroid impacts have played a crucial role in shaping Earth’s history, and scientists believe that past collisions may have even influenced human evolution. “Asteroid impacts have taken place many times in Earth’s history. 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,” explained Dr Lan Dai, co-author of the study.
The most infamous asteroid impact, which struck the Yucatán Peninsula around 66 million years ago, created the Chicxulub crater and is widely believed to have triggered the mass extinction that wiped out the dinosaurs. Earth has largely avoided major asteroid collisions since then, thanks in part to the protective effects of Jupiter’s gravity, which helps divert many potential threats.
Despite its potential danger, Bennu has provided scientists with a treasure trove of information about the building blocks of life. Earlier this month, NASA revealed that samples collected from Bennu contain 14 of the 20 amino acids essential for life on Earth, as well as key organic compounds that play a role in forming DNA and RNA.
Additionally, researchers discovered salt minerals formed by the evaporation of water, suggesting that Bennu’s parent body once had liquid water—a fundamental ingredient for life as we know it. These discoveries reinforce the idea that the essential components for life may be common throughout the universe, raising the likelihood that extraterrestrial life exists elsewhere.
While the possibility of Bennu striking Earth is remote, planetary defence experts are already developing asteroid deflection strategies. NASA’s DART mission (Double Asteroid Redirection Test) successfully demonstrated the ability to alter an asteroid’s trajectory in 2022 by crashing a spacecraft into Dimorphos, a small moon orbiting the asteroid Didymos.
If Bennu were ever confirmed to be on a collision course with Earth, similar techniques—such as kinetic impactors or gravitational tractors—could be used to nudge it off course.
Although the threat of Bennu remains low for now, its potential impact serves as a reminder of the cosmic hazards that Earth faces. Scientists are continuously monitoring near-Earth objects (NEOs), and missions like OSIRIS-REx are helping us better understand both the risks and rewards of studying asteroids.
