New Study Reveals Mars’ Atmosphere Could Be Stored Beneath Its Clay Surface

Recent findings indicate that the long-lost atmosphere of Mars might actually be concealed within the planet's clay-enriched crust. This insight offers a fresh perspective on how carbon dioxide (CO2) from Mars’ primordial atmosphere was chemically sequestered in clay minerals, through interactions between water and rock, effectively trapping vast amounts of the planet’s atmospheric gases.

Unraveling the Mystery of Mars’ Ancient Atmosphere

Billions of years ago, Mars was a radically different environment compared to its current cold, arid state. Data collected from rovers and orbiters point to the presence of ancient rivers, lakes, and possibly oceans. To maintain liquid water on the surface, an extensive atmosphere was necessary to retain heat, keeping temperatures above freezing. Most experts agree that early Martian air was rich in carbon dioxide, which functioned as a greenhouse gas, supporting a warmer, potentially life-friendly climate.

Around 3.5 billion years ago, Mars underwent dramatic changes. Its atmosphere thinned dramatically, temperatures fell, and surface water disappeared. For many years, the prevailing theory suggested that solar wind stripped away the atmosphere after Mars lost its magnetic shield. Although this process accounts for some atmospheric loss, recent studies suggest additional factors are at play. Joshua Murray, the lead researcher, notes, “Present-day escape rates can only account for less than 1 percent of the original atmosphere when traced backward.” Hence, scientists have searched for alternative explanations for Mars’ thinning atmosphere.

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Clays as a Possible Atmospheric Reservoir

Led by a team at the Massachusetts Institute of Technology (MIT), the newly published study in Science Advances provides an innovative hypothesis: rather than being lost to space, much of Mars’ atmosphere was chemically absorbed by its surface via reactions involving clay minerals. On Earth, CO2 is similarly captured by smectites, clays formed when ultramafic rocks rich in olivine interact with water.

The research suggests this process likely took place on Mars as water percolated through igneous rocks, converting atmospheric CO2 into methane that was then trapped within clay deposits. This methane could have remained locked in the Martian crust for billions of years. Co-author Oliver Jagoutz explains, “Based on Earth analogs, we demonstrate that similar reactions could have transformed significant amounts of Martian atmospheric CO2 into methane stored in clays.”

These mineral deposits potentially sequestered large volumes of carbon, contributing to Mars’ atmospheric thinning. Employing geological models informed by Earth’s processes, the team estimates the Martian surface could retain around 1.7 bar of CO2—approximately 80% of Mars’ original atmosphere. In other words, a substantial portion of Mars’ early atmosphere may still exist beneath its surface.

Smectite Clays and Their Methane-Trapping Ability

Smectites, abundant on Mars, are layered minerals with high capacities to store gases like CO2 over geological timescales. Unlike Earth’s active tectonics, which recycle carbon stored in clays, the absence of such plate movement on Mars suggests that once sequestered, carbon remains trapped indefinitely in these minerals.

Extensive observations from satellites and rovers confirm widespread clay layers across Mars. Murray states, “There is substantial evidence of thick clay sheets on Mars, with nearly 80 percent of spectral data from orbit detecting high-surface-area clay minerals. Clays have even been identified in craters as deep as 17 kilometers.” These vast clay deposits imply a long-term absorption of atmospheric CO2, offering a viable explanation for Mars’ lost atmosphere.

The initial chemical process involves water reacting with olivine, yielding serpentine, which gradually transforms into smectites. During this reaction, hydrogen liberated bonds with CO2, forming methane that becomes trapped within the clays. This trapped methane is effectively prevented from reentering the atmosphere.

Impact on Upcoming Mars Missions and Science

Recognizing that Mars’ atmosphere could be preserved underground opens new avenues in planetary science and exploration. If methane and CO2 remain stored in the clays, these gases might be harvested as valuable resources. Methane, specifically, offers potential as a fuel source for crewed missions, aiding long-term habitation and exploration of the Red Planet.

This understanding also enriches our knowledge of Mars’ climatic evolution. By analyzing the interplay of water, rock, and atmospheric gases, scientists can reconstruct the planet’s shift from a wet, warm habitat into today’s frozen desert. Murray adds, “Given the abundance of Martian clays, the question is how much methane they can store,” which could provide crucial insights into the original atmospheric makeup and its decline.

Moreover, this research challenges existing ideas about atmospheric loss in rocky planets, suggesting that surface mineral sequestration might be a common mechanism. Such a process could apply to other celestial bodies with early atmospheres, expanding our comprehension of planetary development beyond Mars.

Is Atmosphere Restoration on Mars Possible?

Although the prospect of extracting methane from Mars’ clay reservoirs is exciting for future endeavors, the researchers emphasize that more research is necessary to precisely quantify the CO2 and methane preserved beneath the planet’s surface. Even if recoverable, releasing these gases back into the atmosphere will require advanced technology not yet developed. Success in this realm could one day enable terraforming efforts, potentially transforming Mars into a more hospitable world for humans.

In summary, the revelation that Mars’ once-thick atmosphere might be trapped within its clay-rich crust marks a pivotal advancement in planetary science. The study provides a compelling alternative to atmospheric loss theories and unveils promising possibilities for utilizing these hidden gases in future exploration. Continued investigation aims to uncover further details about the Red Planet’s ancient climate and its capacity to support life.