The findings are informed by recent data from NASA's Curiosity rover, which finally detected carbonate-rich rocks-critical clues that had eluded scientists for years. These minerals point to a process where liquid water on Mars' surface reacted with atmospheric carbon dioxide to form rock-bound carbonates, diminishing the planet's greenhouse potential.
"Our models suggest that periods of habitability on Mars have been the exception, rather than the rule, and that Mars generally self-regulates as a desert planet," said Kite, who also serves as a participating scientist on the Curiosity mission.
Despite its similarities to Earth in size, composition, and distance from the sun, Mars failed to sustain the conditions needed for long-term habitability. On Earth, a geologic feedback loop involving carbon cycling stabilizes the climate. Volcanic eruptions release CO2, while weathering reactions draw it down, maintaining a habitable balance. Mars, however, lacks Earth's persistent volcanic activity to replenish lost atmospheric carbon, resulting in long gaps-up to 100 million years-between warm phases.
The breakthrough came as Curiosity climbed Mt. Sharp and detected carbonate deposits that support the model's predictions. "People have been looking for a tomb for the atmosphere for years," said Kite, referring to where Mars' once-thicker atmosphere might have gone.
Study coauthor Benjamin Tutolo of the University of Calgary emphasized the importance of rover-based mineralogy: "The chemistry and mineralogy measurements they provide really are essential in our continuing quest to understand how and why planets stay habitable."
Research Report:Carbonate formation and fluctuating habitability on Mars
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