New research suggests that Mars’ atmosphere may be hiding from view, having been absorbed by minerals in the Red Planet’s clay. If Mars’ gaseous atmosphere “settled on Earth” more than 3 billion years ago, it could explain how Earth’s neighbor became so different from our own, potentially losing its ability to host life.
Scientists know that the Red Planet wasn’t always the barren wasteland that the Mars rovers Perseverance and Curiosity are scouring today. Both of NASA’s rovers have uncovered evidence that copious amounts of water flowed on Mars early in its 4.6-billion-year history. But for Mars to have liquid water, it also had to have an atmosphere that kept that water from freezing. The big question for decades has been: Where did that atmosphere go when it disappeared?
A team of researchers think the answer has been right under the noses (or trajectories) of the Curiosity and Perseverance rovers all along. In a paper published in the journal Science Advances , they argue that while water was present on the Red Planet, it may have seeped through certain types of rocks and set off a slow chain reaction that sucked carbon dioxide out of the atmosphere. This could have been converted into methane, a form of carbon, and locked up in Mars’ clay surface.
“Based on our results on Earth, we show that similar processes may have been occurring on Mars and that abundant amounts of atmospheric carbon dioxide may have been converted to methane and stored in clays,” said Oliver Jagoutz, a team member and professor of geology in the Department of Earth, Atmospheric and Planetary Sciences at MIT, in a study published in the journal Nature. statement“It is possible that this methane may still be present and perhaps be used as an energy source on Mars in the future.”
Related to: NASA’s Perseverance rover on Mars is on its way to conduct its first study of the rim of the Dox Castle crater.
How Earth Pointed the Way in the Mystery of Mars’ Atmosphere
Working in his group at MIT, Jagoutz and his colleagues began their research not on Mars, but on our own planet. The scientists were trying to determine the geological processes that drive the evolution of Earth’s hard, brittle outer layer, which surrounds the crust and upper mantle, known as the lithosphere.
The researchers focused on a type of surface clay mineral called smectite, which is extremely efficient at trapping carbon. A single grain of smectite is made up of so many folds that carbon can settle into it and remain undisturbed for billions of years.
On Earth, smectite rocks are formed by the movement of tectonic plates that hold the continents together. This tectonic activity has lifted smectite rocks to the surface of our planet. When exposed to the surface, these folded clay minerals absorb carbon dioxide, removing this greenhouse gas from the atmosphere and helping our planet cool over millions of years.
As Jagütz looked at the surface of the Red Planet, the team shifted focus to Mars, noticing a similar thick material spread across Earth’s neighbor.
The discovery of smectite rocks on Mars raised an important question: How did this folded clay mineral form, given that the Red Planet lacks tectonic activity? To answer this question, the team turned to what they know about the geological history of Earth’s neighbor.
One piece of evidence was the detection of low-silica igneous rocks in the Red Planet’s crust called “ultramafic rocks.” On Earth, these igneous rocks are known to form thick rocks when eroded or “weathered” by water. On Mars, there is evidence of ancient rivers where water could have flowed and interacted with the underlying rocks.
The team then used knowledge of how water and igneous rocks interact on Earth to create a model that could be applied to Mars. The model would reveal whether water interacted with deep ultramafic rocks on Mars in a way that would produce the thicketite rocks on the surface today.
Using this model, the scientists found that over the course of a billion years, water may have seeped through the crust and reacted with a magnesium-iron silicate mineral abundant in igneous rocks called peridotite. This mineral is rich in iron, which oxygen from the water likely bonded with in the process, releasing hydrogen. This oxidized iron may have helped give Mars its distinctive red color.
The released hydrogen then probably combined with carbon dioxide in the water to form methane, a reaction that slowly transformed the olivine into another iron-rich rock called serpentine. As the serpentine continued to react with the water, it may eventually have formed smectite.
“These smectite clays have a great capacity to store carbon,” lead researcher and MIT graduate student Joshua Murray said in the statement. “So we used existing knowledge about how these minerals are stored in clays on Earth, and went on to say, if the surface of Mars has this much clay, how much methane can you store in that clay?”
The team discovered that to store the amount of methane needed to extract most of the carbon dioxide from the Martian atmosphere, the Red Planet would have to be covered in a layer of smectite more than 3,600 feet (1,100 meters) deep.
“We found that estimates of global clay volumes on Mars are consistent with the fact that much of Mars’ initial carbon dioxide was stored as organic compounds within the clay-rich crust,” Murray concluded. “In some ways, Mars’ lost atmosphere may be hiding right under our noses.”
The team’s research was Posted on September 25 In the journal Science Advances.
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