Dinosaurs: A global dust cover has led to mass extinction on Earth, according to a study

A new study suggests that a global layer of dust caused by an asteroid impact 66 million years ago led to the mass extinction of dinosaurs and many other species. Researchers from Purdue University in Indiana, United States, have detailed how this event transformed Earth into a hellish landscape, with extreme heat and widespread fires playing key roles in the mass extinction. The findings were published in the journal Journal of Geophysical Research: Biogeosciences. The asteroid, roughly the size of Mount Everest, struck the region of the Yucatán Peninsula in present-day Mexico, creating the Chicxulub crater. This impact wiped out approximately three-quarters of all species on Earth, including most dinosaur populations. The collision vaporized rock and soil over more than 1,000 cubic kilometers, forming material that circled the planet. As this debris entered Earth's atmosphere, countless droplets of molten rock, known as spherules, formed. These particles generated heat as they fell through the atmosphere, while a fine layer of dust enveloped the globe. This dust layer acted like a blanket or insulating cover over the Earth, trapping heat and preventing it from escaping into space. Additionally, the dust reflected the thermal radiation from the falling spherules back toward the Earth’s surface, intensifying the warming effect. This process created a kind of planetary grilling, leading to widespread wildfires that burned grass, tree needles, lichens, and possibly even wood across vast areas of land. According to the lead author of the study, physicist Brandon C. Johnson, the kinetic energy from the impact had to go somewhere, ultimately being converted into heat that cooked the Earth's surface and everything on it. He stated that it was not the shock wave from the impact or the fireball that caused the mass extinction, those effects did not reach far enough. Instead, it was the global spread of this vaporization veil, the dust cloud, that turned the event into a planetary catastrophe. Without the dust cloud, Johnson wrote, many organisms would still have perished, but it wouldn't have been a global extinction event. The dust layer was so opaque that it trapped almost all the heat from the falling spherules near the planet's surface. The researchers compared the dust to a lid on a pot, explaining that due to this layer, anything unable to find shelter was essentially baked or fried. Survivors likely took refuge underground or in water, finding protection there. Similar dust particles form during modern forest fires. On Earth, the conditions probably resembled hell, according to the researchers. The clouds blocked sunlight, making the surface appear dark to any creature that could not see infrared light. Only a reddish glow from the wildfires would have been visible. However, very little life would have remained to witness such a scene. The dust particles formed were about 2.5 micrometers in size, similar to smoke particles from today's forest fires, which primarily cause long-term health issues. The study highlights the environmental impact of such tiny particles, both in ancient times and in contemporary contexts.