A recent study suggests that the atmosphere of Mars, once dense and capable of sustaining liquid water, might have been absorbed by clay minerals present in the soil of the Red Planet over 3 billion years ago.
This hypothesis could explain how Mars became an arid and hostile planet, so different from Earth, potentially losing its ability to host life. Scientists know that Mars, in the past, was not the desolate landscape we know today.
The NASA rovers Perseverance and Curiosity have found evidence indicating the presence of abundant water on the planet in its early stages, about 4.6 billion years ago.
However, to maintain water in a liquid state, Mars must have had an atmosphere that prevented freezing.
The question that has fascinated researchers for decades is: where did this atmosphere go? A team of researchers has recently proposed an explanation, based on investigations conducted directly from the traces left by the rovers on Mars.
According to a study published in Science Advances, the water present on Mars might have reacted with particular types of rock, absorbing carbon dioxide (CO₂) from the atmosphere and trapping it in clay soils, transforming it into methane. Oliver Jagoutz, a professor of geology at MIT, explained that, based on similar processes observed on Earth, enormous amounts of atmospheric CO₂ on Mars could have been sequestered in clay minerals, particularly in smectites, rocks that trap carbon for billions of years.
This trapped methane might still be present and, according to scientists, could represent a future energy resource for missions on Mars. Smectites are particularly efficient at trapping carbon, thanks to their ”foldable” structure that allows them to hold molecules for very long periods.
On Earth, these minerals formed thanks to the movements of tectonic plates, which led to their formation and the cooling of our planet through the absorption of CO₂. The discovery of similar minerals on the surface of Mars has raised a crucial question: if Mars does not have significant tectonic activity, how did these smectites form? Researchers found an answer by observing the ultramafic rocks present in the Martian crust, which are known to produce smectites when altered by water.
This process, involving a mineral called olivine, leads to the formation of another mineral, serpentine, during which smectites are also produced. The theory proposed by Jagoutz and his team offers a possible explanation of how Mars lost its atmosphere: slow and complex geochemical reactions, occurring over billions of years, might have absorbed much of the Martian CO₂, transforming it into methane and trapping it in clay soils. This discovery opens new perspectives for understanding the internal and external dynamics of planets, suggesting that complex geochemical processes may have played a significant role in transforming Mars into an arid planet, while Earth maintained its atmosphere and ability to sustain life.
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