Scientists are reconsidering a long-standing belief that water was the primary liquid responsible for shaping Mars’ surface, Space.com reports.
For decades, evidence such as massive outflow channels, ancient river valleys, and lakebeds has suggested that Mars once had abundant water. These features, which resemble those formed by water on Earth, seemed to provide strong support for the idea of a watery past. However, new research proposes that liquid carbon dioxide might also have played a crucial role.
A team of researchers suggests that under the dense atmosphere of early Mars, carbon dioxide could have liquefied and flowed across the surface, carving the landscape in ways similar to water. Their study, published in Nature Geoscience, challenges the prevailing view that Mars’ surface was shaped entirely by water, and instead suggests that liquid carbon dioxide may have also contributed to the planet’s geological history.
Michael Hecht, principal investigator of the MOXIE instrument on NASA’s Perseverance rover, emphasized that while it’s difficult to determine how likely this hypothesis is, the possibility of liquid carbon dioxide should not be dismissed.
“What we can say, and we are saying, is that the likelihood is high enough that the possibility should not be ignored,” Hecht told MIT News.
The researchers draw on earlier experiments from carbon sequestration studies that examined how carbon dioxide interacts with minerals when exposed to brine and supercritical or liquid carbon dioxide. Under the right temperature and pressure conditions, carbon dioxide can exist in a liquid phase that possesses the properties of both a gas and a liquid. These studies have shown that carbon dioxide can chemically react with minerals, forming carbonates, phyllosilicates, and possibly sulfates, which are minerals found on Mars today.
The new theory proposes that the surface features and mineral deposits observed on Mars could have resulted from stable liquid carbon dioxide melting beneath carbon dioxide glaciers or from subsurface reservoirs. This perspective challenges the idea of a singular, warm, wet environment and instead emphasizes the possibility of short-lived, unstable conditions.
Importantly, the researchers do not rule out the potential for both liquid water and liquid carbon dioxide to have shaped the Martian landscape. This dual scenario could provide a more nuanced understanding of Mars’ geological history, suggesting that both liquids may have worked together, rather than one replacing the other.
As scientists continue to study Mars, they stress the importance of expanding beyond Earth-based assumptions and exploring a wider range of possibilities. Hecht concluded:
“Understanding how sufficient liquid water was able to flow on early Mars to explain the morphology and mineralogy we see today is probably the greatest unsettled question of Mars science.
