The asteroid Bennu, measuring 0.31 miles (0.5 kilometers) in diameter and weighing an estimated 74 million tons (67 million metric tons), poses a significant threat to Earth. NASA has identified Bennu as the highest risk asteroid in terms of proximity and potential impact. Despite its relatively small size compared to the 6-mile-wide (10 km) asteroid that created the Chixulub crater and led to the extinction of the dinosaurs 66 million years ago, Bennu still carries a 1 in 2,700 chance of colliding with Earth in the year 2182.
Bennu is believed to have broken away from a larger asteroid between 700 million and 2 billion years ago. In 2016, NASA dispatched the OSIRIS-REx spacecraft to Bennu to collect samples from its surface. These samples returned to Earth in 2023, revealing significant insights into the building blocks of life. The samples contained DNA and RNA components, alongside minerals rich in carbon, sulfur, phosphorus, fluorine, and sodium—elements essential for life.
The potential impact of Bennu raises considerable concerns about the aftermath of such an event. According to supercomputer models, the impact would generate a large dust cloud capable of cooling global temperatures by as much as 7.2 degrees Fahrenheit (4 degrees Celsius). This cooling effect would trigger a series of ecological disruptions, including a 15% decrease in global rainfall and a 30% reduction in global plant photosynthesis.
"It would immediately generate powerful shockwaves, thermal radiation, tsunamis, earthquakes, crater, and ejecta around the collision site," – Timmerman
The immediate effects of a Bennu-sized asteroid impact would cause devastating damages around the impact site. The powerful shockwaves and thermal radiation could lead to catastrophic tsunamis and earthquakes, while the formation of a crater would result in ejecta dispersed across vast areas.
"We focus mainly on the climatic and ecological effects of several hundred million tons of dust into the upper atmosphere from the initial impact," – Timmerman
"The solar dimming due to dust would cause an abrupt global 'impact winter' characterized by reduced sunlight, cold temperature and decreased precipitation at the surface," – Timmerman
The aftermath of such an impact would extend far beyond initial physical destruction. The introduction of several hundred million tons of dust into the upper atmosphere could create a phenomenon known as an "impact winter." This period, marked by reduced sunlight, colder temperatures, and decreased precipitation, could last for more than four years following the impact.
"Severe ozone depletion occurs in the stratosphere due to strong stratospheric warming caused by the solar absorption of dust particles," – Timmerman
In addition to temperature changes, severe ozone depletion could occur in the stratosphere due to strong stratospheric warming. This depletion results from solar absorption by dust particles, further exacerbating the environmental impact.
"The immediate effects of a Bennu-sized asteroid impact would cause devastating damages around the impact site," – Timmerman
