Thin ice caps could have protected lakes on ancient Mars and kept surface water liquid even as the Red Planet’s climate froze, according to new research that could resolve one of the biggest paradoxes in Martian history.
The findings are based on data collected by NASA. Mars Curiosity thief in Gale Crater and then fed through a climate model.
Mars is covered in relics of an aquatic past: dried river and lake beds, canals, deltas, and even what look like the shorelines of an ancient sea. There is a prodigious amount of evidence that liquid water once ran over the surface of the Red Planet, initially leading to the hypothesis that Mars was once warm and wet.
While Mars four billion years ago may have been warmer than it is today, maintaining these temperatures would have required a much thicker amount of carbon dioxide. atmosphere than what is currently seen. This is especially because at that time, the sun It was much fainter and shone only three-quarters as bright as it does today. This simple fact has led planetary scientists to question whether Mars really was ever hot, at least for long periods of time. Subsequently, the warm and wet paradigm of Mars has gradually been replaced by the image of a cold but somehow still wet planet.
This is the apparent paradox that is at the heart of the ancient history of Mars. We see evidence of liquid water even when Mars should have been too cold for liquid water.
So planetary scientists have been looking for ways Mars could have supported liquid water without being very hot.
Moreland teamed up with Sylvia Dee, a Land Climate scientist at Rice University in Texas. Dee had previously developed an Earth climate modeling tool called Proxy System Modeling, which used evidence from tree rings and ice cores to interpret Earth’s climate history.
Of course, Mars has no trees and no ice cores have been obtained, but Moreland, Dee and their colleagues were able to adapt the proxy system model for Mars, using data collected by Curiosity on rock and mineral records to act as surrogates for Mars’ ancient climate. The result was the modeling of lakes on Mars with atmospheric reconstructions and simulations, or LakeM2ARS model.
“It was fun to work on the thought experiment of how a lake model designed for Earth could be adapted to another planet, although this process required a lot of debugging when we had to change, for example, gravity,” Dee said.
Moreland’s team ran 64 different simulations using the LakeM2ARS model, each simulating a hypothetical lake inside the 96-mile-wide (154-kilometer-wide) Gale Crater under conditions believed to have existed on Mars 3.6 billion years ago. Each simulation represented the lake for 30 Martian years, which is equivalent to about 56 Earth years.
In some of the tests, the lake froze completely in winter, but in other cases the lake would develop a thin layer of ice that would thermally insulate the liquid body beneath, like a natural blanket. In spring and summer, the ice sheet melted and then returned the following winter, with the total volume of liquid water in the lake barely changing. In the simulations, this allowed the lake to remain stable for decades as temperatures fell to freezing point.
“When our new model started showing lakes that could last for decades with only a thin layer of ice that disappeared seasonally, it was exciting that we could finally have a physical mechanism that matched what we see on Mars today,” Moreland said.
While the modeling results don’t mean that Mars never had warmer periods during its early history, they do explain how liquid water could have persisted even after those warm periods had ended.
The findings were published in the December 29, 2025 issue of AGU Advances.
