Small lakes on ancient Mars may have remained liquid for decades, even with average air temperatures well below freezing. Using a climate model adapted for Martian conditions, a team of researchers from Rice University discovered that lakes in locations such as Gale Crater, near Mars' equator, could have persisted under thin seasonal ice for at least decades and likely as long as climate conditi Houston TX (SPX) Jan 06, 2026
Small lakes on ancient Mars may have remained liquid for decades, even with average air temperatures well below freezing. Using a climate model adapted for Martian conditions, a team of researchers from Rice University discovered that lakes in locations such as Gale Crater, near Mars' equator, could have persisted under thin seasonal ice for at least decades and likely as long as climate conditions were stable. These findings contribute to resolving a long-standing puzzle in Mars science: Surface features shaped by sustained liquid water coexist alongside climate models suggesting that early Mars was too cold to support such conditions.
The study, published in AGU Advances Dec. 29, offers a new explanation for how lakes might have existed without a warm climate and why ancient Martian lake beds are so well-preserved today.
"Seeing ancient lake basins on Mars without clear evidence of thick, long-lasting ice made me question whether those lakes could have held water for more than a single season in a cold climate," said Eleanor Moreland, a Rice graduate student and lead author of the study. "When our new model began showing lakes that could last for decades with only a thin, seasonally disappearing ice layer, it was exciting that we might finally have a physical mechanism that fits what we see on Mars today."
The researchers adapted a climate modeling tool called Proxy System Modeling, initially developed by Earth climate researcher Sylvia Dee, to reconstruct ancient climates using indirect clues such as tree rings or ice cores.
While Earth has natural markers for these clues, Mars lacks trees or comparable indicators. Instead, the research team used measurements collected by Mars rovers, using the planet's rock and mineral records as proxies for a climate record.
Over several years, they reworked the model for lakes to reflect Mars as it was about 3.6 billion years ago, accounting for differences such as weaker sunlight, a carbon dioxide-rich atmosphere and distinct seasonal patterns.
They ran 64 different test cases in the new Lake Modeling on Mars with Atmospheric Reconstructions and Simulations (LakeM2ARS) model, based on real data from NASA's Curiosity rover in Gale Crater and Mars climate simulations.
Each test simulated a hypothetical lake inside the crater for 30 Martian years, equivalent to approximately 56 Earth years, allowing the researchers to determine whether the lake could realistically remain liquid under those conditions.
"It was fun to work through the thought experiment of how a lake model designed for Earth could be adapted for another planet, though this process came with a hefty amount of debugging when we had to change, say, gravity," said Dee, an associate professor of Earth, environmental and planetary sciences and co-author of the study.
"We were surprised and encouraged by how sensitively the model responded to parameters like atmospheric pressure and temperature seasonality. It shows that with some creativity and experimentation, Earth-origin models can yield realistic climate scenarios for Mars."
In some simulations, the lakes completely froze during colder seasons, whereas in others, the lakes remained liquid and were covered by a thin layer of ice instead of freezing solid. This thin ice acted as an insulating lid, significantly reducing water loss while still allowing sunlight to warm the lake ice during warmer months.
As a result of this seasonal cycling, some simulated lakes barely changed in depth over decades, suggesting that they could be stable for longer durations even with average air temperatures below freezing for much of the time.
"This seasonal ice cover behaves like a natural blanket for the lake," said Kirsten Siebach, an associate professor of Earth, environmental and planetary sciences and co-author of the study.
It insulates the water in winter while allowing it to melt in summer, Siebach said. "Because the ice is thin and temporary, it would leave little evidence behind, which could explain why rovers have not found clear signs of perennial ice or glaciers on Mars," she said.
The findings suggest that early Mars may have supported long-lasting lakes without requiring consistently warm conditions, challenging earlier beliefs that surface water on Mars would require persistent warmth.
If ancient Martian lakes persisted under seasonal ice rather than thick permanent ice, features on Mars that have been difficult to reconcile with past climate models, including preserved shorelines, sediment layers and mineral deposits, may now have clearer interpretations.
The researchers said they look forward to applying LakeM2ARS to other Martian basins to investigate whether similar lakes could have existed elsewhere. They also aim to examine how factors such as changes in atmospheric composition or groundwater circulation might have affected the stability of lake ice over time.
"If similar patterns emerge across the planet, the results would support the idea that even a quite cold early Mars could sustain year-round liquid water, a key ingredient for environments to be suitable for life," Moreland said.
The additional co-authors of this study include Rice undergraduate student Nyla Hartigan, Michael Mischna from the Jet Propulsion Laboratory at the California Institute of Technology, James Russell from Brown University and Grace Bischof and John Moores from York University. The Rice Faculty Initiative Fund and the Canadian Space Agency supported this research.
Research Report: Seasonal Ice Cover Could Allow Liquid Lakes to Persist in a Cold Mars Paleoclimate
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