The wildest scars on our planet are hidden beneath the Yucatán Peninsula(Mexico). The buried crater, over 90 miles in diameter, was created when a massive asteroid struck the planet 66 million years ago and brought a calamitous end to the reign of dinosaurs. The violent shock ignited the forests, triggered a brutal tsunami and expelled so much sulfur into the atmosphere that blocked sunlight, which eventually led to the disappearance of 75% of existing life, including dinosaurs.
That has been the scenario traditionally set by scientists to explain one of the “Five great mass extinctions recorded on Earth”. And that is the hypothesis that supports a new study in which the Center of Astrobiology, of the Higher Council of Scientific Research (CSIC), has participated, after analyzing the rocks extracted from the central area of the Mexican crater.
The “ground zero” material, recovered by the International Ocean Discovery Programme (IODP) in 2016 from an offshore drilling rig, has allowed researchers to describe in unprecedented detail what the first 24 hours were like after the impact. The results are published in the latest issue of the journal Proceedings of the National Academy of Sciences (PNAS). The authors estimate that the asteroid explosion carbonized all vegetation thousands of miles around the impact and triggered an unimaginable tsunami, reaching into inland North America, more than 2,000 kilometers away.
Inside the crater, they found charcoal and also a chemical biomarker of the presence of soil fungi inside or just above layers of sand, a sign of having been deposited by a stream of water. These findings suggest that the charred landscape was dragged into the crater by the retreat ingesting of tsunami waters.
Most of the material that filled the crater in the hours after impact originated in the same place or was swept away by ocean water that flowed back there from the surrounding Gulf of Mexico. In a single day about 130 meters of material were deposited, a dizzying rate of accumulation that shows that the impact was hit by a short-lived hell at the local level, followed by a long period of global cooling. Not in vain Chicxulub means in the Mayan language “devil’s well”.
Absence of sulfur
The team has found molten and fragmented rocks such as sandstones, limestones, and granites, but no sulfur in the core. This was disconcerting, as the area around the crater is filled with sulfur-rich rocks. The finding supports the theory that the asteroid’s impact vaporized the sulfur-rich minerals present at the site of the impact and released it into the atmosphere, which became opaque in sunlight.
This caused profound changes in Earth’s climate, which suffered a global cooling. Researchers estimate that at least 325 billion metric tons would have been thrown into the atmosphere, estimating by the impact. That amount is about ten thousand times higher than all sulfur that was expelled into the atmosphere during the eruption of the Krakatoa volcano (Indonesia) in 1883, which caused an average 2.2 degrees drop in global temperature over five years.
It was precisely this global climate change that caused the mass extinction, not only of the dinosaurs but also of most of the creatures that inhabited the planet at the time.