Mars, the cold desert planet we see today, was once a place where water flowed on its surface billions of years ago. However, around 3.5 billion years ago, the water disappeared, and the thick atmosphere that once protected the planet thinned dramatically. The mystery of where Mars’ atmosphere went has puzzled scientists for years, but recent research by MIT geologists suggests that much of the missing atmosphere could be locked up in the planet’s clay-covered crust.
The team proposes that while water was present on Mars, it could have trickled through certain rock types and set off a slow chain of reactions that gradually drew carbon dioxide out of the atmosphere and converted it into methane, which could be stored in the planet’s clay surface for eons. Drawing on their knowledge of interactions between rocks and gases on Earth, the researchers estimate that Mars’ clay could hold up to 1.7 bar of carbon dioxide, equivalent to 80 percent of the planet’s early atmosphere.
The sequestered carbon on Mars could potentially be recovered and converted into propellant for future missions between Mars and Earth. By examining similar processes that occur on Earth, the researchers suggest that the methane stored in Mars’ clay could serve as an energy source for future endeavors on the Red Planet. This methane could have been formed through interactions between water, rocks, and carbon dioxide over billions of years, providing a renewable energy source for potential human missions to Mars.
The research team at MIT, led by Oliver Jagoutz and recent graduate Joshua Murray, focused on the potential of smectite, a type of clay mineral known to trap carbon effectively, to store vast amounts of greenhouse gases on Mars. On Earth, similar clays have played a role in drawing down carbon dioxide from the atmosphere, suggesting that Mars’ surface clays may have had a similar effect on the planet’s missing atmosphere.
While the formation of smectite on Earth is linked to tectonic activity, there is no such activity on Mars. However, observations of Mars’ surface suggest the presence of ultramafic igneous rocks and geologic patterns resembling terrestrial rivers, providing clues to how clays may have formed on the Red Planet. By modeling the chemical reactions between water and olivine-rich rock on Mars, the team estimated the potential for Mars’ crust to store significant amounts of methane within its clay-rich surface.
The researchers found that if Mars is covered with a layer of smectite 1,100 meters deep, this amount of clay could store a substantial quantity of methane, equivalent to most of the carbon dioxide that has disappeared from the planet’s atmosphere over time. Their findings suggest that Mars’ missing atmosphere could be hidden in plain sight, concealed within the planet’s clay-rich crust. This study sheds light on the potential for Mars’ clay minerals to play a crucial role in understanding the fate of the planet’s atmosphere and in harnessing renewable energy sources for future exploration efforts.