About 66.5 million years ago, an asteroid about 10 km wide collided with Earth. The 180 km diameter Chikshulub Crater formed at the impact site is located on the Yucatan Peninsula. During the collision, a lot of sulfur was released into the air: a cloud of sulfur dioxide rose to the height of the stratosphere and blocked access to Earth by sunlight. This led to a sharp cooling of the planet’s surface and a mass extinction of fauna, including dinosaurs.

In addition, later sulfur fell to the ground along with acid rain, which also affected the fauna. Marine life was particularly hard hit, as sulfur leaches from land into the sea and its content is so high.

But scientists previously misjudged the sulfur concentration in Earth’s atmosphere, according to a new study published in the Proceedings of the National Academy of Sciences. It was much higher, which means that its effects on the planet are more devastating and lasting for a long time.

The discovery was made by chance while exploring the Brazos River Valley in Texas near Chickshulub Crater. The researchers collected several unscheduled sediment samples, and laboratory analysis showed the presence of extremely unusual sulfur isotopes with a slight variation in mass. Most anomalous sulfur isotopes are found in Cretaceous-Paleogene sediments, but also occur in the Early Paleogene.

Such sulfur isotopes are formed by interacting with ultraviolet light. This means that they can occur in two situations: if there is no oxygen on Earth, or if sulfur enters the stratosphere.

But since the oxygen atmosphere on Earth has existed for about 2.3 billion years, the best explanation would be stratospheric photolysis of SO₂.

All of this has led scientists to suggest that the sulfur cloud is much larger and that the sulfur concentration is much higher than previously thought. According to preliminary estimates, the amount of sulfur released into the atmosphere after a collision with an asteroid ranged from 30 to 500 gigatons.

According to climate models, this was to reduce the temperature at the Earth’s surface by 2-8 ⁰C. Also, this decline has and continued for at least several decades, which led to the global extinction in the Cretaceous. But scientists now believe this data needs to be listed and clarified.

Overall, new information confirms the theory of the dominant role of sulfur gases in the formation of climate on Earth after a collision with an asteroid. This rejects the hypothesis that the extinction was caused by volcanic activity in the Deccan Traps, a large volcanic formation found in modern India.

The site of the asteroid’s fall, where large deposits of sulfur-containing limestone were found, played a role in the disaster, according to the study’s authors. Presumably, if the collision had occurred elsewhere on the planet, events would have developed in a different scenario.

To imagine how sulfur is released into the atmosphere, it is enough to mention the eruption of the volcano – these are similar processes. Sulfur from volcanoes is usually neutralized by sulfates, but in Antarctica, where there are no such neutralizers, for example, isotopes of sulfur can accumulate in snow and ice.