Dry ice, not water, carves Mars' canyons, new study finds

For years, scientists have debated whether enigmatic channels that wind through the dunes of Mars were the result of the passage of liquid water in the past or some other process. Now, a team of Dutch researchers has put an end to that controversy: It wasn't the water, but the dry ice —frozen carbon dioxide— is responsible for these formations.

The study, led by the Dr. Lonneke Roelofs from Utrecht University with the master's student Simone Visschers, has managed to recreate the behavior of CO₂ under Martian atmospheric conditions in the laboratory. The results, published this week in Geophysical Research Letters, show how Blocks of dry ice sliding on the sand can excavate deep, winding channels, exactly the same as those observed by NASA satellites.

“It was like watching sandworms Dune, “Move beneath the surface,” Roelofs said, comparing the phenomenon to the iconic scene from the science fiction saga.

Experiments in a “Martian chamber”

The researchers conducted their tests in a unique facility: a “Mars chamber” Located at the Open University of Milton Keynes (United Kingdom), it is capable of reproducing the low atmospheric pressure and extreme thermal differences of the red planet.

Inside this chamber, they placed blocks of dry ice on simulated Martian sand, tilted at different angles to observe their behavior. They discovered that the blocks shifted and reacted in two very different ways, depending on the slope of the terrain.

En steep slopes (more than 25 degrees), the dry ice slid quickly, carving straight and shallow channels. However, in gentler slopes (less than 22,5 degrees) Something completely different was happening: the gas released by the sublimation of CO₂ was trapped under the block, increasing the pressure until it was released in a series of localized explosions that threw grains of sand several meters into the air.

This process caused the blocks to They will “bury” themselves in the surface and advance as if crawling under the sand., forming sinuous channels with raised edges, identical to those observed by NASA's HiRISE camera in Martian craters.

The role of carbon dioxide and the Martian winter

On Mars, winter temperatures in the mid-latitudes of the southern hemisphere can fall below -120 ° C, allowing carbon dioxide from the atmosphere to freeze and accumulate on the dunes in layers of up to 70 centimeters thick.

When the Martian spring arrives and sunlight warms the sand, the CO₂ blocks begin to break and slide downhill, reaching sizes of up to one meter. The heat of the soil causes the instant ice sublimation, which goes directly from solid to gas, generating a film of pressurized air that acts as a lubricating layer under the block.

“In our simulation, we saw the high-pressure gas violently escaping in all directions, lifting the sand and pushing the block forward,” Roelofs explained. This process excavated trench after trench, leaving sand ridges on both sides of the channel, a topographic signature that exactly matches satellite observations.

Satellite evidence confirms the model

The data from orbital topography from the Russell Crater on Mars corroborate the results of the experiment. There, the researchers observed shallow channels near dune crests which gradually transform into curved grooves that become deeper as they descend, just the pattern that was reproduced in the laboratory.

The team's additional simulations showed that, under the lower Martian gravity, sand grains ejected by CO₂ sublimation can travel more than half a meter horizontally, sufficient distance to create the lateral ridges or “edges” that characterize these channels.

This reinforces the hypothesis that gaseous forces, without the intervention of liquid water, are capable of generating complex relief forms, something that was previously attributed exclusively to water erosion.

A discovery that changes the geological history of Mars

For more than two decades, scientists have interpreted the calls gullies or "linear gullies" as evidence of a wet past on Mars, when the planet would have hosted seasonal rivers or streams. However, the Dutch team's results show that These channels can be formed today, without water, through purely physical processes.

The discovery forces review the narrative on Martian climate evolution, as it suggests that Not all erosive activity requires liquid water"Our experiments show that solid carbon dioxide, when sublimated, can sculpt the surface as effectively as water on Earth," Roelofs noted.

The finding also explains why These structures appear mainly in the polar and mid-southern regions of Mars., where conditions are ideal for the accumulation and seasonal release of dry ice.

Implications beyond Mars

The study could have implications beyond the Red Planet. Researchers note that Similar processes could be occurring on other icy worlds in the solar system.as the Europa, Triton or Titan, where volatile ices abound and can sublimate under certain conditions of solar radiation.

In these environments, erosion caused by expanding gases could play a more important role than previously thought, generating reliefs that mimic those produced by liquids. This poses new challenges for interpreting planetary images and searching for traces of water or life.

“We now know that gas can sculpt a planet’s surface in surprisingly complex ways,” Roelofs said. “This discovery forces us to rethink how we understand geological activity on worlds where water is scarce or nonexistent.”

A new way of seeing Mars

The research from Utrecht and Milton Keynes marks a turning point in Martian exploration. By demonstrating that dry ice can act as a active geological agent, scientists offer an elegant and testable explanation for one of the greatest enigmas of modern planetary geology.

In the future, missions such as ExoMars or NASA's next orbiters could incorporate sensors designed to directly detect the presence and dynamics of the Seasonal CO₂ on the Martian surface, confirming whether these processes continue to occur today.

If so, Mars would not only be a planet shaped by the past, but also by active forces in the present, invisible but powerful, capable of carving their landscapes with a material as strange as it is beautiful: dry ice.