The asteroid that wiped out the dinosaurs 66 million years ago also plunged the planet into a long-lasting winter, according to a new study. The researchers found that the dust from the impact blocked out most of the sunlight and reduced the global temperature by 15 degrees Celsius for up to two years.
The asteroid, estimated to be about 10 kilometers in diameter, slammed into the Yucatan Peninsula in Mexico, creating a crater that is now 180 kilometers wide and 20 kilometers deep. The collision released an enormous amount of energy, equivalent to more than a billion atomic bombs. It triggered massive earthquakes, tsunamis, wildfires, and shockwaves that devastated the environment and killed many living creatures.
But the most lethal effect of the impact may have been the global climate change that followed. The asteroid vaporized and shattered the rocks at the impact site, ejecting about 2,000 gigatonnes of dust into the atmosphere. This dust cloud spread around the world and blocked most of the sunlight from reaching the surface. Without sunlight, plants could not perform photosynthesis and produce oxygen and food. This disrupted the food chain and caused widespread starvation and extinction.
The evidence from North Dakota
The researchers based their findings on a paleontological site in North Dakota, called Tanis, that preserved evidence of the post-impact conditions. The site contains fossils of fish, plants, and other organisms that were buried by sediment from the impact-induced tsunami. The sediment also contains glassy spheres called tektites, which are formed by molten rock ejected from the crater. The tektites are mixed with fish scales and bones, indicating that they fell from the sky while the fish were still alive.
The researchers analyzed the chemical composition of the tektites and compared them with samples from the Chicxulub crater. They found that they matched well, confirming that they originated from the impact site. They also measured the size distribution of the tektites and used computer simulations to estimate how long they stayed in the air before falling to the ground. They found that the smallest tektites, which are about 0.8 micrometers in diameter, could have remained airborne for up to 15 years.
The researchers also ran paleoclimate simulations based on the amount and size of the dust particles. They found that the dust cloud could have reduced the global temperature by 15 degrees Celsius for up to two years, and by 5 degrees Celsius for up to 15 years. This would have created a dark and cold world, where only a few species could survive.
The implications for mass extinction and evolution
The study provides new insights into how the Chicxulub impact caused one of the most severe mass extinctions in Earth’s history. It shows that dust played a more important role than previously thought, compared to other factors such as sulfur and soot. The dust cloud not only cooled down the planet, but also altered the atmospheric circulation and precipitation patterns, affecting the hydrological cycle and nutrient cycles.
The study also suggests that some organisms may have adapted to the post-impact conditions by evolving new traits or behaviors. For example, some plants may have developed mechanisms to cope with low light levels, such as increasing their leaf size or chlorophyll content. Some animals may have shifted their diet or habitat preferences, such as eating fungi or living underground. These adaptations may have given them an evolutionary advantage over their competitors, leading to new branches of life.
