At a Glance
- A new study proposes that carbonate rocks discovered by NASA rovers are the key to understanding why Mars lost its surface water and became a desert world.
- Scientists modeled a negative feedback loop where liquid water formed carbonate rocks that trapped atmospheric carbon dioxide, cooling the planet and limiting further water stability.
- This cycle created brief, intermittent “oases” of habitability on the Martian surface, followed by immense, hundred-million-year-long periods of extreme cold and dryness.
- Unlike Earth’s stable climate, maintained by active volcanism, Mars has a much weaker volcanic cycle and cannot replenish the atmospheric carbon dioxide lost to rock.
- The model suggests Mars self-regulated as a desert planet, which has significant implications for where and how scientists should search for signs of ancient life.
A new study offers a compelling explanation for why Mars is a barren desert. At the same time, Earth teems with life, indicating a planetary self-regulation system that has prevented long-term surface habitability. Research published Wednesday in the journal Nature uses the recent discovery of carbonate-rich rocks by NASA’s Curiosity rover to model a unique climate history for the red planet. This model suggests that while liquid water once flowed on Mars, it did so only in brief, geographically isolated episodes, creating temporary “oases” in an otherwise relentlessly cold and dry world.
The key to this new understanding lies in a negative feedback loop involving sunlight, water, and carbon dioxide. On early Mars, as the sun’s luminosity gradually increased, it warmed the planet enough for ice to melt into liquid water. This water then reacted with rocks to form carbonates, a process that pulls carbon dioxide—a potent greenhouse gas—out of the atmosphere and sequesters it in the planet’s crust. This atmospheric thinning would cool the planet back down, shutting off the flow of liquid water until the cycle could slowly restart. Unlike Earth, which has a robust volcanic cycle that replenishes atmospheric carbon dioxide, Mars’s weaker volcanism could not keep up, dooming it to a colder, drier state.
According to the model developed by planetary scientists, these wet periods were remarkably fleeting, followed by vast stretches of up to 100 million years of desert conditions. This pattern of intermittent habitability would have made it extremely difficult for any potential life to survive on the surface. Edwin Kite, the study’s lead author from the University of Chicago, explained that these findings suggest Mars was a planet of “blips of habitability in some times and places,” but never sustained the stable, water-rich environment seen on Earth.
This research reframes the search for ancient Martian life, suggesting that evidence may be confined to specific layers of rock corresponding to these brief periods of habitability. Both NASA’s Curiosity and Perseverance rovers have now found evidence of these crucial carbonate rocks, bolstering the model’s predictions. The ultimate test, scientists say, will be analyzing Martian rock samples returned to Earth, a goal that both the United States and China are pursuing. Determining whether life took hold during these short-lived oases could provide profound insight into how easily life can arise in the universe.
References
- Kite, E. S., Tutolo, B. M., Turner, M. L., Franz, H. B., Burtt, D. G., Bristow, T. F., Fischer, W. W., Milliken, R. E., Fraeman, A. A., & Zhou, D. Y. (2025). Carbonate formation and fluctuating habitability on Mars. Nature, 643(8070), 60–66. https://doi.org/10.1038/s41586-025-09161-1
- Lawler, D. (2025, July 5). Why is there no life on Mars? Rover finds a clue. Phys.Org; Phys.org. https://phys.org/news/2025-07-life-mars-rover-clue.html
