Groundbreaking Discussion in Nature Geoscience

A groundbreaking discussion in the latest edition of *Nature Geoscience* challenges the long-held belief that liquid water was the primary agent shaping Mars' surface. Researchers point to the numerous dry river channels and lake beds on the Martian surface, previously interpreted as evidence of ancient water flow. However, a new analysis argues that liquid carbon dioxide (CO2) could have played a significant role too, if not a more dominant one than water.

Research Led by Michael Hecht

Led by Michael Hecht, the principal investigator for NASA's MOXIE instrument aboard the Mars Rover Perseverance, this provocative paper raises critical questions about Mars' climatic history. Hecht, who is also a research scientist at MIT's Haystack Observatory, emphasizes, “Understanding how sufficient liquid existed on early Mars to account for its surface features is probably the biggest unsolved mystery in Martian research. Our findings propose another avenue to explore.”

Challenging Traditional Views

Traditionally, the mineral evidence gleaned from orbit and landers has strongly favored water as the liquid responsible for the Martian landscape. Nonetheless, the authors of the study argue that liquid CO2 could produce similar mineral alterations as detected on Mars. Recent studies in carbon sequestration—where CO2 is captured and stored—involved reactions that occur rapidly enough to support the idea that liquid CO2 could be present, creating sedimentary structures like those seen on the Red Planet.

Three Scenarios for Liquid CO2

The authors suggest that the conditions on early Mars might have favored CO2 condensation over water melting. They propose three scenarios where liquid CO2 could exist: as a stable liquid on the surface, as a product of melting beneath CO2 ice, or in subsurface reservoirs. Each scenario's validity hinges on the planet's historical CO2 inventory and temperature conditions.

Caution on Laboratory Conditions

However, Hecht and his team caution that current laboratory conditions used for their findings—specifically environments above room temperature with high pressure—differ drastically from the cold, low-pressure settings expected on ancient Mars. They argue for more detailed studies to evaluate whether similar reactions would occur under Mars-like conditions.

Speculation and Future Research

“This speculation is still just that—speculation,” Hecht admits. “Nevertheless, the probability that liquid CO2 contributed to the Martian landscape is significant enough that we cannot afford to ignore it.”

Looking Ahead

As the intrigue surrounding Mars continues to grow, these insights may redefine our understanding of the planet’s geological and atmospheric evolution, as scientists march forward in their quest to uncover the secrets of the Red Planet. Will we someday come to view Mars not just as a world of water, but also as a realm shaped by liquid carbon dioxide? The debate is just beginning!