Experts on what could happen if Asteroid Bennu strikes Earth and triggers ‘global catastrophe’

A 500-metre-wide asteroid could strike Earth in 157 years and set off a chain of events that could plunge the planet into winter and devastate plant life, according to new research.

The asteroid, named Bennu, passes close to Earth every six years. It is listed as one of NASA’s “potentially hazardous objects,” ranked third on the Sentry list of potential Earth impact events. The space rock, which stands taller than the Empire State Building, has a one-in-2,700 chance of hitting our home planet on September 24, 2182.

Climate scientists in South Korea have modelled what would happen if such a collision took place. Their “worst-case scenario” analysis involved injecting up to 400 million tonnes of dust and debris into the stratosphere.

They found that a collision could trigger major climate disruptions, with the dust “dimming the Sun” and triggering a global temperature drop of 4C, a 15 per cent drop in rainfall and a 32 per cent reduction in the ozone.

This would effectively plunge the planet into winter, devastating plant life and impacting food production. "The abrupt impact winter would provide unfavourable climate conditions for plants to grow, leading to an initial 20 to 30 percent reduction of photosynthesis in terrestrial and marine ecosystems," said Lan Dai of Pusan National University in South Korea. "This would likely cause massive disruptions in global food security."

The researchers used a supercomputer at the university's IBS Centre for Climate Physics to simulate a 500-metre asteroid colliding with Earth. They found the climate effects of an asteroid of this magnitude would last up to three or four years after impact.

However, the researchers say an impact of this size isn’t uncommon. "On average,