For years, scientists have puzzled over a contradiction on Mars.
The planet’s surface is covered with features that look unmistakably like ancient lake beds—shorelines, layered sediments, and minerals that usually form in water.
Yet most climate models suggest that early Mars was far too cold for liquid water to last on the surface. A new study offers a simple but powerful solution: thin ice.
Researchers from Rice University have found that small lakes on ancient Mars could have remained liquid for decades, even when average air temperatures stayed well below freezing.
The key was a thin, seasonal ice cover that acted like a natural insulating blanket.
The study, published in AGU Advances, helps explain how liquid water and a cold Martian climate could exist at the same time.
The team focused on areas near Mars’s equator, including Gale Crater, where NASA’s Curiosity rover has gathered years of geological data. Normally, scientists assumed that if lakes existed there, they must have frozen solid or disappeared quickly. But the new simulations show a different picture.
Graduate researcher Eleanor Moreland, the study’s lead author, wondered whether lakes really needed a warm climate to survive.
Using a climate model originally designed for Earth, the team carefully reworked it to reflect Mars as it was about 3.6 billion years ago. That meant accounting for weaker sunlight, lower gravity, a carbon dioxide–rich atmosphere, and extreme seasonal changes.
Because Mars has no trees or ice cores to reveal its climate history, the researchers relied on rocks and minerals measured by rovers as clues to past conditions. They then ran dozens of simulations of hypothetical lakes inside Gale Crater, each lasting 30 Martian years—about 56 Earth years—to see whether liquid water could realistically persist.
In many cases, the lakes did freeze during colder seasons. But in others, something surprising happened. Instead of freezing solid, the lakes developed a thin layer of ice that formed in winter and melted away in warmer months. This ice sharply reduced evaporation and heat loss, while still allowing sunlight to pass through and warm the water beneath.
The result was stability. In some simulations, lake levels barely changed over decades, even though air temperatures stayed below freezing for much of the year. The ice acted like a lid, protecting the water without leaving thick, permanent ice behind.
This detail is important because Mars rovers have not found strong evidence of large glaciers or long-lasting ice sheets in these ancient lake regions. Thin, seasonal ice would leave little trace, making it consistent with what scientists actually see on the ground today.
The findings suggest that early Mars did not need to be warm and Earth-like to host long-lived lakes. Instead, even a cold planet could sustain surface water under the right conditions. That helps explain the remarkably well-preserved shorelines, sediment layers, and minerals found across the Martian surface.
Looking ahead, the researchers plan to apply their model to other Martian basins and explore how changes in the atmosphere or groundwater might have affected lake stability. If similar results appear elsewhere, it would strengthen the idea that Mars once had widespread, long-lasting bodies of liquid water.
That possibility matters for more than geology. Liquid water is one of the key ingredients for life. If lakes could persist on a cold Mars for decades or longer, the planet may have been more hospitable than scientists once believed.
Source: KSR.
