It’s widely acknowledged that the Earth was a cold, dark place after a giant meteor, measuring roughly six miles across, struck Mexico about 66 million years ago, which many believe triggered what is known as the end-Cretaceous mass extinction.
Now, new research using state-of-the-art computer simulations paints a more detailed picture of this period and how long-lasting cooling and a mixing of the oceans may have spelled the end for the dinosaurs.
The results of the new study discounted the competing theory that it was large-scale volcanic eruptions, as opposed to the meteor’s impact, that led to the extinction.
“Our results show that the impact must have played a significant role in the mass extinction,” lead study author Julia Brugger from the Potsdam Institute for Climate Control told Fox News.
The model assumed that tiny droplets of sulfuric acid in the atmosphere caused the long-term cooling after the comet hit. It’s long been posited that it was dust particles thrown into the air from the meteor strike that lethally blocked the sun, but dust wouldn’t last long enough in the atmosphere to cool the Earth for several years. Sulfate aerosols have a longer cooling effect due to their more sustained time in the atmosphere.
“The target rock, which was struck by the asteroid, contained sulfur,” Brugger explained. “After the impact, sulfur bearing gases evaporated and formed sulfate aerosols high up in the atmosphere.”
For Brugger, the most surprising result of the study was the magnitude of the cooling. When the acid droplets blocked the sun, it caused the Earth’s surface air temperature to drop by at least 79 degrees Fahrenheit. Even the annual mean temperatures of the tropics went from 80 to 41 degrees. The global average temperature was below freezing for about three years, which was obviously bad news for life on Earth. Dinosaurs used to a tropical climate froze while their food supplies withered and died. It would take 30 years for the climate to recover from the cooling.
“This is based on basic physical laws, but I still find it fascinating that an accident like this asteroid impact can completely change climate for a couple of years,” Brugger said. “It really illustrates how fragile our climate system is.”
Another surprise was the meteor impact’s disruption of ocean circulation. The ice caps expanded and surface waters cooled down, becoming denser and heavier. While these cooler water masses sank into the depths, warmer water from deeper ocean layers rose to the surface. The warmer waters carried nutrients that likely led to massive blooms of algae that may have been toxic.
“The model simulations of our study allow us to observe a disturbance of the ocean circulation and this leads to a nutrient transport to the surface ocean,” Brugger said. “This could have caused an algal bloom and it is conceivable that these algal blooms produced toxic substances, further affecting life at the coasts.”
This toxic algae– as well as sulfuric acid from the meteor strike mixing into the oceans– might’ve been what led to the deaths of marine life, which would include creatures like the ammonites (marine mollusk animals). Creatures living on the coast would have been greatly affected as well.
While the comet strike likely meant the end for the dinosaurs, it did make way for the evolution of the human species. And though extinction was cold and dark for the prehistoric creatures, it’ll likely be quite toasty for us.
“It's a certain irony that today the most immediate threat is not from natural cooling but from human-made global warming,” Brugger said.