Is Mars' missing atmosphere hiding in plain sight?

Mars, known as the Red Planet, wasn’t always the uninviting desert we see today. There’s a lot of concrete evidence suggesting that water flowed freely on this mysterious planet billions of years ago. In the ancient past, the atmosphere of Mars was possibly every bit as ardent and earth-like as the world we live in.

But the question remains – What happened to this planet that it turned into the cold, barren desert we see today?

Mystery of Mars’ missing atmosphere

One of the biggest mysteries surrounding Mars’ 4.6-billion-year history is understanding the fate of its atmosphere.

Once rich with carbon dioxide, it was substantial enough to prevent water from freezing over. But, around 3.5 billion years ago, the water vanished, and the atmosphere mysteriously thinned out, leaving behind only a wisp of its former self.

Now, two MIT geologists believe they have an intriguing answer to this vexing question – the key to Mars’ missing atmosphere could be in the planet’s clay-rich crust.

Atmosphere lost in Mars’ crust

In a fascinating research paper appearing in the journal Science Advances, the scientists suggest that the Martian clay-crust may be the tomb of the planet‘s lost atmosphere.

The experts argue that as water was present on Mars, it could have seeped through specific rock types, triggering a slow chain of reactions. These reactions drew carbon dioxide from the atmosphere, converting it to methane that could be preserved for ages within the planet’s clay surface.

This theoretical conceptualization draws parallels from similar processes happening right here on Earth. Using their knowledge of how rocks and gases interact in terrestrial conditions, the researchers proposed analogous Martian processes.

The implications of their findings are staggering. The experts estimate that Mars’ clay could hold up to 1.7 bar of carbon dioxide, equivalent to approximately 80% of Mars’ original atmosphere.

The future of Martian Missions

One of the exciting implications of the research is the possibility of using this trapped Martian carbon as propellant for future Mars-Earth missions. Our capacity to harness this buried resource could change the game for interplanetary travel.

Professor Oliver Jagoutz from MIT’s Department of Earth, Atmospheric, and Planetary Sciences (EAPS) co-authored the study alongside recent EAPS graduate Joshua Murray.

Based on their Earth-based findings, the researchers propose that similar processes likely happened on Mars and that substantial amounts of atmospheric CO2 could have transformed into methane and been captured within clays.

Mars atmosphere trapped in clay

Professor Jagoutz’s team at MIT dedicates their efforts to understanding the geological processes that govern Earth’s lithosphere.

In 2023, the team focused on a type of surface clay mineral called smectite, known as an efficient carbon trap. On Earth, smectite clay helps extract enough carbon dioxide from the atmosphere to cool the planet over millions of years.

While investigating Mars, Jagoutz noticed that the Martian surface was also blanketed in smectite clays. Could these clays have had a similar effect on Mars? Could they be holding onto Mars’ lost carbon?

“We know this process happens, and it is well-documented on Earth. And these rocks and clays exist on Mars,” said Professor Jagoutz. “So, we wanted to try and connect the dots.”

How did these clays form on Mars?

Unlike Earth, where smectite is an outcome of continental plates shifting and uplifting, Mars has no similar tectonic activity.

To understand how these clays formed on Mars, the team relied on what is known about the planet’s history and composition. Based on observations of Mars’ surface and existing knowledge of rock chemistry, they developed a model to explain the formation of Martian clays.

The model hypothesized that over a billion years, as water percolated through the crust filled with carbon dioxide, it reacted with a mineral called olivine abundant in the crust.

This process released hydrogen and formed the red oxidized iron, giving Mars its iconic red hue. The resulting hydrogen combined with the carbon dioxide, forming methane.

As this process continued, olivine transformed into another iron-rich rock known as serpentine, which further reacted with water to form smectite.

Where is Mars’ missing atmosphere?

The team’s model suggests that if the Martian surface has a layer of smectite 1,100 meters deep, this much clay could store an enormous amount of methane, equivalent to most of the carbon dioxide thought to have disappeared since planet Mars dried up.

“We find that estimates of global clay volumes on Mars are consistent with a significant fraction of Mars’ initial CO₂ being sequestered as organic compounds within the clay-rich crust,” said Murray. “In some ways, Mars’ missing atmosphere could be hiding in plain sight.”

Significance of the study

This research has undoubtedly provided a promising path to solving one of the greatest Martian mysteries.

As we continue to explore Mars, and perhaps even turn it into a launchpad for further space exploration, understanding its geological history becomes ever more crucial. Thanks to scientists like Jagoutz and Murray, we are a step closer to unraveling the secrets of the Red Planet.

The findings promise to impact the future of space exploration, adding yet another exciting chapter to the story of Mars – a planet that continues to fascinate us with its mysteries.

The research was partly funded by the National Science Foundation.

The study is published in the journal Science Advances.

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