About 65 - 66 million years ago, our planet experienced the last great mass extinction (the so-called Cretaceous-Paleogene extinction). It led to the death of about one-sixth of all terrestrial species. Terrestrial vertebrates were particularly affected by the event. Almost all species weighing over 25 kg did not survive a global catastrophe, including dinosaurs. The destruction of old ecosystems has dramatically spurred the evolution of animal groups such as birds and mammals. It is believed that it was the Cretaceous-Paleogene extinction that set off the chain of events that ultimately led to the emergence and dominance of the planet Homo Sapiens.
Currently, most scientists associate the Cretaceous-Paleogene extinction with the consequences of the impact of a large asteroid. An obvious candidate for the site of its fall is the Chicxulub crater in the Yucatan Peninsula, which was formed about 65 million years ago. Its diameter is about 180 km, the size of its body was 10 km. The impact energy is estimated at 100 teratons of TNT, nearly two million times the most powerful thermonuclear bomb ever tested.
A team of scientists from the US National Center for Atmospheric Research, with support from NASA and the University of Colorado at Boulder, has created the most detailed computer model to assess the impact of this impact. According to their findings, during the collision, about 15 trillion tons of ash, dust and soot were thrown into the earth's atmosphere. For comparison, during the eruption of the Tambor volcano, which led to the so-called. "A year without summer", about 140 billion tons of material was thrown away.
The ingress of such a huge amount of matter into the atmosphere led to the fact that for the next 18 months the planet plunged into darkness. The surface illumination actually dropped to the level of the moonlit night. The temperature of the oceans decreased by 11 degrees, and the continents - by 28 degrees Celsius. Photosynthesis has practically stopped.
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At the same time, ash trapped in the upper atmosphere absorbed solar energy, heating the surrounding air. As a result, the temperature of the stratosphere reached 200 degrees Celsius, which led to the destruction of the ozone layer. As the dust settled, the harsh ultraviolet light was able to reach the earth's surface unhindered. Over time, the ozone layer recovered, and average temperatures returned to their usual values. But not all species survived to this.
Despite the fact that the new model is much more detailed than previous studies of the effects of the impact, its authors emphasize that it also has certain limitations. For example, it is based on today's Earth's climate and the percentage of gases in the atmosphere, while their composition was slightly different during the time of the dinosaurs. Also, the model does not account for dust and soot emissions from impact-induced forest fires and volcanic activity. So in the future, we should expect the emergence of even more accurate models of the consequences of the collision, which changed the course of all earth's history.
