By Will DunhamWASHINGTON (Reuters) – Bennu, a rocky object classified as a near-Earth asteroid, is currently on its close approach to our planet every six years at a distance of about 186,000 miles (299,000 km). However, scientists warn that there is a one-in-2,700 chance of a collision with Earth in September 2182. What would the consequences of such an impact be? According to new research based on computer simulations of an asteroid impact similar in size to Bennu (roughly three-tenths of a mile or 500 meters in diameter), the aftermath would be devastating.
In addition to immediate destruction, the impact would release 100-400 million tons of dust into the atmosphere, leading to disruptions in climate, atmospheric chemistry, and global photosynthesis lasting three to four years. “The dust-induced solar dimming would trigger a sudden global ‘impact winter’ characterized by reduced sunlight, cold temperatures, and decreased precipitation on the surface,” explained Lan Dai, a postdoctoral research fellow at the IBS Center for Climate Physics (ICCP) at Pusan National University in South Korea and the lead author of the study published in Science Advances this week.
The researchers found that in the worst-case scenario, Earth’s average surface temperature would drop by approximately 7 degrees Fahrenheit (4 degrees Celsius), rainfall would decrease by 15%, plant photosynthesis would be reduced by up to 20-30%, and the planet’s ozone layer – which shields against harmful solar ultraviolet radiation – would be depleted by 32%.
The impact of an asteroid the size of Bennu on Earth’s surface would create a powerful shockwave, earthquakes, wildfires, thermal radiation, a massive crater, and eject substantial amounts of debris into the atmosphere, according to the researchers. Aerosols and gases released into the upper atmosphere would have long-lasting effects on climate and ecosystems.
Under the unfavorable climate conditions following the impact, plant growth on land and in the ocean would be hindered. Dai noted, “Unlike the slow recovery of land plants over two years, ocean plankton would rebound within six months – and even flourish due to diatom blooms triggered by iron-rich dust entering the ocean.”
The researchers also highlighted severe stratospheric ozone depletion due to the strong warming caused by dust particles absorbing solar radiation. While the study did not delve into the potential human casualties of such an event, Dai mentioned that the death toll would “largely depend on the impact location.”
Bennu, known as a “rubble pile” asteroid, is believed to be a collection of rocky material rather than a solid mass. It is a fragment from a larger celestial body that formed near the beginning of the solar system roughly 4.5 billion years ago. NASA’s OSIRIS-REx spacecraft collected samples from Bennu in 2020, revealing chemical compounds hinting at the potential role
The primitive components that paved the way for the rise of living beings are found within the basic elements of our world. Throughout the vast timeline of Earth’s existence, asteroids have intermittently collided with our planet, often resulting in catastrophic consequences. One such instance occurred approximately 66 million years ago when an asteroid measuring between 6 to 9 miles (10 to 15 km) in diameter impacted the region near Mexico’s Yucatan Peninsula. This event led to the extinction of around three-quarters of the Earth’s species and marked the conclusion of the dinosaur era. In the year 2022, NASA undertook a preliminary mission in planetary defense, utilizing its automated DART spacecraft to alter the trajectory of the asteroid Dimorphos. The ultimate aim is to be prepared for potential future scenarios where an asteroid may pose a threat of colliding with Earth.
According to Timmermann, the probability of an asteroid similar in size to Bennu striking Earth is relatively low, standing at 0.037%. Yet, despite this low probability, the potential consequences of such an impact would be severe, potentially resulting in widespread and long-lasting food shortages on our planet. Additionally, it could lead to climate disruptions comparable to those witnessed only during some of the most significant volcanic eruptions over the past 100,000 years. Timmermann emphasizes the importance of acknowledging and addressing this risk, highlighting the necessity of proactive measures to safeguard Earth from potential future asteroid impacts.
(Reported by Will Dunham, Edited by Rosalba O’Brien)
