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Simulations of a potential collision between Earth and a hill-sized asteroid in the next century have shown how severe the blow would be for humanity, and what we would need to survive such a catastrophe. It's been a long time since the last major asteroid impact, but that doesn't mean we're safe. Space is full of rocky bodies, and many of them are moving in orbits that could lead them to collide with our planet.
One such object is the asteroid Bennu, which was recently targeted by a sample collection mission. It could collide with Earth in as little as 157 years, in September 2182. The probability of this scenario is small—only a 1 in 2700 chance (or 0,04%), but it is not zero.
To prepare for the worst, climate scientists from South Korea have modeled the consequences of such a collision. After all, the last major impact, which occurred 66 million years ago (the Chicxulub meteorite), is associated with the extinction of the dinosaurs. Although Bennu is much smaller (500 meters in diameter) compared to the Chicxulub asteroid (10–15 km), its effects would still be devastating.
Climate impacts
“Our simulations, which account for the release of up to 400 million tons of dust into the stratosphere, show significant disruptions to climate, atmospheric chemistry, and global photosynthesis,” write Lan Dai and Axel Timmerman of Pusan National University. In particular, the average global temperature would drop by 4°C and precipitation would decrease by 15%.
The researchers used the Aleph supercomputer to model the effects of a Bennu impact, taking into account the impact on terrestrial and marine ecosystems, which has not been considered in previous studies. The most destructive will not be the impact itself, but its aftermath. The dust ejection will darken the Sun, which will significantly reduce the level of photosynthesis, disrupting the functioning of ecosystems and the climate balance.
Ozone depletion and famine
In addition to decreasing temperatures and precipitation, ozone levels could drop by 32%, making terrestrial flora even more vulnerable.
“A sharp cooling will lead to a deterioration in plant growth conditions, reducing photosynthesis by 20–30%,” Dai notes. “This is likely to cause serious disruptions to global food security.”
However, the study also revealed an unexpected positive effect: while terrestrial plants will take a long time to recover, algae in seas and lakes will grow faster due to increased levels of iron in atmospheric dust.
Will humanity survive the catastrophe?
It's difficult to say exactly how often Earth has been hit by such impacts, as erosion gradually erodes the craters. However, researchers estimate that such events occur once every 100 to 200 years.
“It is possible that our ancestors have already experienced such catastrophic events that could have influenced the evolution of humanity and even our genetic code,” Timmerman notes.
Humanity, like cockroaches, has an excellent chance of surviving this catastrophe, albeit in much smaller numbers and with significantly altered living conditions. The study is published in the journal Science Advances.
