What if Bennu hit Earth?<\/h3>\n
Asteroid Bennu is a 1,640-foot-wide (500-meter-wide) space rock that has a 1-in-2,700 chance of hitting Earth in September 2182. Two scientists from the IBS Center for Climate Physics at Pusan National University in South Korea have modeled what might happen if Bennu struck Earth. They said on February 5, 2025, the results could be worse than the dinosaur-killing asteroid. Their simulations showed severe disruptions in climate, atmospheric chemistry and global photosynthesis. For three to four years, temperatures would drop, precipitation would decrease and some 32% of our protective ozone layer could be destroyed.<\/p>\n
The immediate impacts of such an asteroid strike would be an increase in thermal radiation, earthquakes and tsunamis. But the researchers zeroed in on the long-lasting climatic effects. The new research looked at what would happen to our climate and how that would impact both terrestrial and marine ecosystems.<\/p>\n
The scientists published their peer-reviewed results in the journal Science Advances<\/em> on February 5, 2025.<\/p>\n The asteroid that killed off the dinosaurs, Chicxulub, was probably some 20 times larger than Bennu. So how could the result of a Bennu strike be worse?<\/p>\n The researchers used four different models for amounts of dust injected into our atmosphere: 100 tons, 200 tons, 300 tons and 400 tons. In all these scenarios, the paper said that nearly 90% of total dust nanoparticles stay in the atmosphere for almost 1 year. But by the second year, dust particles fall out of the atmosphere more quickly in the 400-ton scenario. That\u2019s because more dust means they\u2019re more likely to bump into each other more quickly, creating larger particles that fall out of the atmosphere sooner. The Chicxulub event probably had some 2 million tons of dust ejected into the atmosphere, which would have allowed for a quick removal of 99% of the dust within 3 months.<\/p>\n So the scientists concluded that a medium-sized asteroid, like Bennu, is more likely to produce an amount of dust that would hang around in the atmosphere for longer. The paper said: <\/p>\n Our simulations suggest that dust particles have much longer atmospheric residence times than for the Chicxulub impact.<\/p>\n<\/blockquote>\n The major impacts from a Bennu-sized asteroid strike would last for three to four years. In the 400-ton scenario, we could expect temperatures around the globe to drop about 7 degrees Fahrenheit (4 degrees C). Precipitation would decrease by some 15%. And we would lose some 32% of our protective ozone layer. These results would all vary locally.<\/p>\n Lead author Lan Dai of Pusan National University said: <\/p>\n The abrupt impact winter would provide unfavorable climate conditions for plants to grow, leading to an initial 20 to 30% reduction of photosynthesis in terrestrial and marine ecosystems. This would likely cause massive disruptions in global food security.<\/p>\n<\/blockquote>\n Surprisingly, the plankton in the ocean would recover much more quickly than terrestrial life. Instead of a slow recovery like terrestrial life, plankton would be mostly recovered in six months. Not only that, but they\u2019d see an increase above normal conditions. Co-author Axel Timmerman of Pusan National University said: <\/p>\n We were able to track this unexpected response to the iron concentration in the dust.<\/p>\n<\/blockquote>\n If the asteroid is iron-rich and hits an iron-rich area of Earth, this material that blasts into the atmosphere could then add iron to areas of the ocean that are otherwise low in this key nutrient for algae. Thus, the increase in iron would trigger algae blooms.<\/p>\n Dai said: <\/p>\n The simulated excessive phytoplankton and zooplankton blooms might be a blessing for the biosphere and may help alleviate emerging food insecurity related to the longer-lasting reduction in terrestrial productivity.<\/p>\n<\/blockquote>\n Scientists have already undertaken a mission to Bennu and retrieved samples for study. NASA said on January 29, 2025, that the samples contain molecules that, at least on Earth, are the building blocks of life. As Paul Scott Anderson reported for EarthSky:<\/p>\n Bennu contains all 5 of the nucleobases that form DNA and RNA on Earth. The asteroid also contains 14 of the 20 amino acids found in known earthly proteins. But \u2013 in a fundamental way \u2013 the chemical structure of the molecules in Bennu aren\u2019t like those on Earth. Earthly amino acids found in living organisms typically have a \u201cleft-handed\u201d chemical structure. Bennu appears to contain nearly equal amounts of \u2018left-handed\u2019 and their \u201cright-handed,\u201d or mirror-image, forms. What does it mean? Scientists aren\u2019t sure yet.<\/p>\n<\/blockquote>\nWorse than the dinosaur-killer?<\/h3>\n
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How bad would it get?<\/h3>\n
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A more-resilient ocean<\/h3>\n
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A mission to Bennu<\/h3>\n
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