Dinosaurs went extinct around 66 million years ago, and it is widely believed that a giant asteroid was the reason. However, the exact turn of events has been a bit of a mystery, as a single strike — although devastating — may not have been enough to completely wipe out all life on Earth.
Climate scientists have worked out that it may have been the aftermath of the asteroid hit that was the final straw for the dinosaurs. According to a new study, droplets of sulfuric acid formed high up in the air after the impact of the asteroid, blocking out sunlight for years.
The new study, published in the journal Geophysical Research Letters, shows how the aftermath of the asteroid strike would have impacted any surviving life on Earth. Plants would all have died due to the lack of light, and this would have had a direct and fatal impact on the rest of the food chain.
Previous theories have focused on the dust ejected by the impact, but new computer simulations show that sulfuric acid droplets are much more likely. The acid could also have mixed into the oceans, severely disturbing marine life too.
"The big chill following the impact of the asteroid that formed the Chicxulub crater in Mexico is a turning point in Earth history," said Julia Brugger, lead author of the study from the Potsdam Institute for Climate Impact Research (PIK), in a statement. "We can now contribute new insights for understanding the much debated ultimate cause for the demise of the dinosaurs at the end of the Cretaceous era."
A shock to the system
Things were a lot toastier on Earth when the dinosaurs were around, at least until the asteroid arrived. After the strike, the average temperature fell from 27 degrees to 5 degrees Celsius in the tropics. Dinosaurs were used to living in a tropical climate, and had evolved and adapted to it. A a 22 degree drop would be quite a shock to the system, especially as the researchers say the global average temperature was below freezing point for about three years.
Ice caps expanded, ocean circulation became disturbed, and surface waters cooled down making the seas denser and heavier. Marine ecosystems were severely affected, which probably contributed to the extinction of species like ammonites — marine mollusc animals that you often see as fossils.
According to the study, it took about 30 years for the climate to recover, and by then the damage to dinosaur life had been done. This, of course, left the space for a new era of organisms to thrive that would evolve into humans.
"It is fascinating to see how evolution is partly driven by an accident like an asteroid's impact — mass extinctions show that life on Earth is vulnerable," said co-author Georg Feulner who led the research team at PIK. "It also illustrates how important the climate is for all lifeforms on our planet. Ironically today, the most immediate threat is not from natural cooling but from human-made global warming."
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