A new study led by Edwin Kite, a planetary scientist from the University of Chicago, offers a fresh perspective on why Mars has transformed into a desert over time. The research, published in Nature on July 2, suggests that while Mars once had liquid water due to solar brightening, it tends to revert to desert conditions unlike Earth, which remains habitable.
This theory builds on findings from NASA's Mars Science Laboratory Curiosity mission. In April, Curiosity discovered carbonate-rich rocks that might explain the disappearance of Mars' atmosphere. "For years, we’ve had this huge unanswered question for why Earth has managed to keep its habitability while Mars lost it," said Kite. He added that their models indicate that habitable periods on Mars were rare and that the planet generally self-regulates as a desert.
Mars and Earth share similar compositions—both are rocky planets with carbon and water—and yet they have diverged significantly in terms of climate and habitability. Evidence such as river-carved valleys suggests Mars was once warm enough for liquid water. "Fortunately, Mars preserves a trace of that environmental catastrophe in the rocks on its surface," said Kite.
Earth maintains stability through a system cycling carbon between the atmosphere and rocks. On Mars, however, this cycle is self-limiting due to slow volcanic activity. As the sun gradually brightens over billions of years, any emerging liquid water would cause carbon dioxide to become trapped in rocks, pushing Mars back toward being cold and barren.
The team developed models illustrating these transitions between wet periods and extended dry spells lasting millions of years—intervals too long for sustaining life. This explanation gained traction after Curiosity found carbonate-rich rocks at Mt. Sharp earlier this year.
"People have been looking for a tomb for the atmosphere for years," Kite noted about the quest to find where Martian carbon went since initial rover tests didn't detect carbonate-rich rocks until now.
Study co-author Benjamin Tutolo emphasized the importance of having rovers like Curiosity on-site: "The chemistry and mineralogy measurements they provide really are essential in our continuing quest to understand how and why planets stay habitable."
Contributors to this study included researchers from several institutions such as NASA Goddard Space Flight Center, NASA Ames Research Center, California Institute of Technology, Brown University, Jet Propulsion Laboratory alongside UChicago postdoctoral researcher Madison L. Turner.
Citation: “Carbonate formation and fluctuating habitability on Mars.” Kite et al., Nature, July 2, 2025.
Funding: NASA.