2024-02-12 20:25:04
During its 4.5 billion year history, the Earth has experienced several episodes of extreme glaciation where it was entirely covered in ice –a model called “Snowball Earth” or “Ice Ball Earth”. The most recent one occurred 600 million years ago.
How could the Earth turn into a gigantic ball of ice? Until now, the most popular hypothesis was that volcanoes that emitted enormous quantities of sulfur dioxide caused extreme cooling in temperatures. Now, a once-ignored hypothesis is making a comeback thanks to a new study, published on January 9, 2024 in the journal Science Advances and relayed by National Geographic. The new suspect would be an asteroid, whose cataclysmic impact would have disrupted our entire planet 600 million years ago.
How can we explain that a large extraterrestrial rock can cause such cooling that the entire surface of land and oceans is covered with a thick layer of ice?
Enough to disfigure the Earth
When they impact the ground of our planet, (large) asteroids break up into a large quantity of rocks, which are then thrown into the sky. This debris can notably be composed of sulphide minerals, which transform into aerosols reflecting sunlight in the stratosphere. Depending on the amount of aerosols in the stratosphere, the Earth can cool very quickly.
For this new study, the scientists simulated their hypothesis on a computer. They then injected aerosols loaded with sulfate (i.e. the equivalent of rock fragments from the asteroid) into the stratosphere, while varying the climatic contexts. The researchers found that by simulating the experiment in an era when the Earth was warm, the planet cooled without freezing. On the other hand, simulations of ice age periods have left our planet no chance: it has transformed into a giant snowball. In other words, by simulating the experiment based on the climate of the pre-industrial era (before the year 1850), the Earth did not freeze, unlike simulations on the Neoproterozoic era.
Professor Christian Köberl, author of the study, explains that it is “much harder to cause a snowball when it’s so hot on Earth” like in our time. On the other hand, “it’s possible” at times when the planet is already cold, he says.
For now, the study only offers a theoretical approach to what might have happened 600 million years ago. The geoscientist Thomas Gernon explains “that there is currently no geological evidence to show that this occurred”. However, nothing prevents us from finding a crater corresponding to the impact of this famous asteroid, even after 600 million years of erosion and tectonic movements. Christian Köberl calls himself “enticed” to the idea that irrefutable geological evidence could one day confirm their hypothesis. On the other hand, you may not share the optimism of the researchers, since Minmin Fu, also author of the study, warns: “The effects of a large asteroid impact followed by a period of glaciation would be disastrous and could lead to the extinction of humanity.”
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