Secrets in the clay

A recent study suggests that Mars' early thick atmosphere may be locked up in the planet's clay-rich surface, offering new insights into the Red Planet's ancient climate and potential for habitability. Conducted by a team of researchers from MIT, the study suggests that the clays on Mars could contain significant amounts of carbon dioxide, which once constituted a dense atmosphere. This discovery not only sheds light on the Red Planet's geological history but also opens up exciting possibilities for future space exploration missions.

Background

Mars’ atmosphere has been one of the most intriguing features of our universe, acting as a barrier between us and understanding the history and composition of possibly one of the first habitable planets. Mars' atmosphere is over 100 times thinner than Earth's and is primarily composed of carbon dioxide, nitrogen and argon gases. Oxidized dust particles kicked up from the Martian surface fill the atmosphere turning Mars' skies a rusty tan color, according to NASA. Water exists on Mars but the atmosphere is too thin for it to last long on the surface in a liquid state. Instead, water on Mars is found below the surface of the polar regions as water-ice and also as seasonal briny water flows down hillsides and crater walls. However, the planet hasn’t always been this barren, with composition tracing to an era of flourishment. Early in its history Mars had a thick enough atmosphere for water to run on its surface. According to NASA, some surface features suggest that Mars experienced huge floods about 3.5 billion years ago. 

Early Mars likely resembled Earth, with a thicker atmosphere that could have supported lakes, rivers, and possibly even oceans. The planet's surface shows evidence of ancient valleys, riverbeds, and lake basins, indicating that liquid water was once abundant. Scientists believe that Mars' early atmosphere was rich in carbon dioxide, which would have created a greenhouse effect, keeping the planet warm enough to maintain liquid water on its surface. Over time, Mars' atmosphere underwent significant changes. The loss of Mars' magnetic field, which occurred approximately 4.2 billion years ago, left the planet vulnerable to solar wind. This stream of charged particles from the sun gradually stripped away the Martian atmosphere. Without a protective magnetic field, the atmosphere thinned, reducing surface pressure and causing temperatures to drop. This transformation turned Mars from a potentially habitable planet to the cold, arid world we observe today. Today's Martian atmosphere is a thin shell, composed of 95% carbon dioxide, with traces of nitrogen and argon. The atmospheric pressure is only about 610 pascals (0.088 psi), which is less than 1% of Earth's atmospheric pressure at sea level. This thin atmosphere cannot support liquid water on the surface, causing any water that does appear to quickly evaporate or freeze. Despite its thinness, Mars still experiences weather phenomena, including dust storms that can envelop the entire planet, seasonal changes, and even frost.

Details About the Study

However, recently a part of this mysterious atmospheric hidden veil has been lifted by a group of scientists. A recent study by MIT researchers, published in the journal Science Advances on September 25, 2024, suggests that Mars' early thick atmosphere might be locked within its clay-rich surface. The team, led by Joshua Murray and Professor Oliver Jagoutz, proposes that water on Mars could have set off a chain reaction, drawing carbon dioxide (CO2) out of the atmosphere and converting it into methane stored within clay minerals1. This process, similar to some interactions observed on Earth, could have sequestered up to 1.7 bar of CO2, equivalent to around 80% of Mars' initial atmosphere. The researchers believe that this sequestered carbon could potentially be recovered and used as propellant for future missions between Mars and Earth. 

“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,” Murray says. “In some ways, Mars’ missing atmosphere could be hiding in plain sight.”

“Where the CO2 went from an early, thicker atmosphere is a fundamental question in the history of the Mars atmosphere, its climate, and the habitability by microbes,” says Bruce Jakosky, professor emeritus of geology at the University of Colorado and principal investigator on the Mars Atmosphere and Volatile Evolution (MAVEN) mission, which has been orbiting and studying Mars’ upper atmosphere since 2014. Jakosky was not involved with the current study. “Murray and Jagoutz examine the chemical interaction of rocks with the atmosphere as a means of removing CO2. At the high end of our estimates of how much weathering has occurred, this could be a major process in removing CO2 from Mars’ early atmosphere.”

This work was supported, in part, by the National Science Foundation.

By analyzing data from Mars rovers and orbiters, the researchers identified extensive clay deposits across the Martian surface that potentially contain up to 1.7 bar of CO2. This amount is equivalent to approximately 80% of Mars' original thick atmosphere, which played a crucial role in maintaining warmer and wetter conditions on the planet billions of years ago. The study's findings provide compelling evidence that the disappearance of Mars' atmosphere could be partly explained by this sequestration process, offering new insights into the planet's geological and atmospheric history.

Implications

The real question that the layman might ask in this scenario is - what does this mean? Well, there are many implications for this discovery. Firstly, there are practical implications for not just future Mars missions, but also extraterrestrial voyages. The sequestered carbon in Martian clays could be an invaluable resource for creating fuel and other essential materials, potentially enabling long-term human exploration and colonization of the Red Planet. To elaborate, there is a growing interest and investment in CO2 utilization technologies, particularly in the areas of carbon capture and utilization (CCU) and carbon dioxide removal (CDR). (38,49,100−102) CCU technologies aim to convert CO2 into value-added products, such as chemicals, fuels, and building materials. Utilizing this could fuel space exploration. If successful, space-derived materials might translate into a significant increase in the global GDP, with the injection of new wealth generated off-planet. The private space economy is particularly poised to benefit, as private enterprises spearhead the movement towards space industrialization, branching out economic growth beyond Earth’s limits. 

The implications of the recent MIT study on Mars’ ancient atmosphere also extend to our understanding of the Red Planet. By revealing that significant amounts of carbon dioxide could be sequestered in Mars' clay-rich surface, the study provides compelling evidence that Mars once had a much thicker atmosphere, capable of supporting liquid water and potentially life. This new perspective helps to reconstruct Mars' climatic history, offering insights into how the planet transitioned from a warm, wet environment to the cold, arid world we see today. Additionally, understanding the interactions between Martian water and minerals aids in identifying past habitable conditions and guides the search for ancient microbial life. These findings not only enhance our scientific knowledge but also inform future missions, highlighting the potential of using Martian resources to support human exploration and settlement.

In conclusion, this groundbreaking study conducted by MIT researchers offers a transformative perspective on Mars' atmospheric history and its potential for supporting life. By uncovering the significant role of clay minerals in sequestering carbon dioxide, the research not only explains the dramatic reduction of Mars' ancient atmosphere but also opens up innovative possibilities for future missions. As we continue to unravel the mysteries of the Red Planet, these findings will guide scientists and explorers in their quest to understand Mars' past and harness its resources for future human settlement. The potential of utilizing Martian clays for fuel production marks a significant step towards sustainable interplanetary travel, bringing us closer to making Mars a second home.

Raaghav Modukuri | Writer, The STEM Review