Researchers at Rice University have developed a climate model showing that small lakes on early Mars could remain liquid for decades beneath thin seasonal ice, despite freezing temperatures. This finding addresses a key puzzle in planetary science about evidence of water on a seemingly cold Red Planet. The study suggests such lakes may have melted and refrozen annually without fully solidifying.
Small lakes on early Mars, around 3.6 billion years ago, might have endured for decades even as average air temperatures dipped far below freezing, according to a new study from Rice University. Published in AGU Advances, the research adapts an Earth-based climate modeling framework to simulate Martian conditions, particularly in Gale Crater near the planet's equator.
The team, led by graduate student Eleanor Moreland, modified the Proxy System Modeling approach—originally used for reconstructing Earth's ancient climates via proxies like tree rings or ice cores—into a tool called LakeM2ARS. This model incorporates Mars-specific factors such as reduced sunlight, a carbon dioxide-heavy atmosphere, and unique seasonal variations. Drawing on data from NASA's Curiosity rover, including rock formations and mineral deposits, they ran 64 scenarios simulating a hypothetical lake over 30 Martian years, equivalent to about 56 Earth years.
Results indicate that in certain conditions, lakes stayed liquid under a thin ice layer that formed seasonally. This ice served as an insulator, trapping heat to prevent full freezing while permitting sunlight to warm the water during milder periods, thus minimizing evaporation and depth changes over time.
"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," Moreland said. "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."
Co-author Kirsten Siebach added, "This seasonal ice cover behaves like a natural blanket for the lake. It insulates the water in winter while allowing it to melt in summer. 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."
The discovery challenges prior views that liquid water required prolonged warm spells on Mars. Instead, stable lakes under seasonal ice could account for preserved geological features like shorelines, layered sediments, and minerals. Future work will test the model on other Martian basins to assess broader implications for past habitability, as liquid water remains crucial for potential life-supporting environments.
The study was supported by the Rice Faculty Initiative Fund and the Canadian Space Agency, with co-authors from institutions including NASA's Jet Propulsion Laboratory and Brown University.