For decades, scientists have scoured Mars for traces of life—from ancient riverbeds to lake basins and channels that hinted at the planet’s wetter past. Now, new research suggests that something eerily lifelike may be reshaping the planet’s surface—giant blocks of dry ice that seem to “burrow” through dunes almost like living organisms.
According to a new study published in Geophysical Research Letters and led by researchers from Utrecht University, the strange sinuous channels seen on Martian dunes, once thought to be carved by flowing water, are actually sculpted by blocks of carbon dioxide ice that slide and dig their way downhill as they sublimate, or vaporize.
The discovery not only redefines how scientists understand these Martian landforms, but also challenges long-held assumptions about how much water—and by extension, how much potential for life Mars might once have had.
“We tried out various things by simulating a dune slope at different angles of steepness. We let a block of CO2 ice fall from the top of the slope and observed what happened,” co-author and Earth scientist at Utrecht University, Dr Lonneke Roelofs, said in a press release. “After finding the right slope, we finally saw results. The CO2 ice block began to dig into the slope and move downwards just like a burrowing mole or the sandworms from Dune. It looked very strange!”
For decades, linear dune gullies have puzzled planetary scientists. Found across mid-latitude dunes between 36° and 70° south, these narrow, often winding trenches snake down steep slopes and end in pit-shaped depressions.
Early researchers proposed that they were formed by debris flows, essentially muddy avalanches fed by melting subsurface ice. That interpretation carried the exciting implications that if liquid water once flowed here, Mars might have supported life.
However, in the mid-2000s, spacecraft like NASA’s Mars Reconnaissance Orbiter began capturing time-lapse images showing something strange. These gullies were active today, changing from one Martian winter to the next. And instead of melting water, the timing lined up with the seasonal thaw of carbon dioxide frost, the same dry ice that makes up much of Mars’ polar caps.
To test how this might work, Dr. Roelofs and her colleagues built a miniature Martian dune inside a special low-pressure chamber known as “George” at the Open University in the U.K. The chamber was filled with fine sand and pumped down to 700 pascals, roughly the same atmospheric pressure as Mars. From there, the researchers released small blocks of CO₂ ice onto the sloped surface and filmed what happened next.
The results showed that under Martian conditions, the dry ice didn’t just slide—it burrowed. As it vaporized, gas built up beneath the block, generating enough force to eject sand in explosive bursts. The block slowly dug itself into the dune, carving deep, snaking channels with steep, raised levees and crescent-shaped pits, features that perfectly matched the mysterious gullies seen from orbit.
In contrast, when the same experiment was performed under Earth’s atmospheric pressure, the blocks merely skidded across the surface, leaving shallow ruts.
Researchers explain that the key difference lies in Mars’ ultra-thin atmosphere. With so little air resistance, sublimating CO₂ gas can flow and expand far more violently than on Earth, blasting sand grains several meters into the air. This process, they say, produces two distinct behaviors:
On steep slopes (greater than about 25°), the blocks slide quickly, carving shallow, straight channels. However, on gentler slopes, below roughly 22.5°, the same blocks slow down and begin to burrow, pushing sediment outward and forming the deeper, sinuous gullies that had baffled researchers for years.
“The burrowing movement helps explain the formation of unique characteristics of linear dune gullies: high levees, deep channels, channel sinuosity, and pit-shaped endings,” researchers write.
Satellite topography from Mars’ Russell Crater supports the idea. There, researchers observed shallow gullies near dune crests that transition into deeper, curved channels farther downslope, exactly what researchers’ experiments reproduced in the lab.
The team even modeled how far the explosive gas bursts could fling sand. Under Mars’ lower gravity, ejected grains could travel more than half a meter horizontally, enough to build the prominent levees seen from orbit. Larger blocks, like the meter-wide chunks of CO₂ ice spotted by NASA’s HiRISE camera, could theoretically toss sand over 10 meters, matching the real-world dimensions of Martian gullies.
While the mechanism may sound alien, the implications are surprisingly Earth-like. By showing that gases alone can carve complex landforms, the study challenges the assumption that sinuous channels always indicate liquid erosion.
“Our results show that linear dune gullies on Mars are carved by both sliding and burrowing blocks of CO2 ice,” researchers write. “This implies that water has no role in the formation of linear dune gullies on Mars and that morphological features like sharp bends/sinuous channels are not definitive proof of the action of liquids on planetary surfaces.”
These results mean planetary scientists may need to rethink how they interpret surface features on other icy worlds, like Europa, Triton, or even Titan, where volatile ices can sublimate and flow in strange ways.
The findings also highlight just how dynamic Mars still is. Far from a dead world, its dunes are alive with motion, reshaped each spring by the bizarre dance of evaporating dry ice. Each winter, CO₂ frost settles across the dunes.
When sunlight returns, it turns directly into gas, breaking loose chunks that slide or dig their way down the slope, excavating channels and flinging sand skyward. Over the years, repeated cycles can deepen the gullies and build towering levees.
According to the researchers, this ongoing process could even help refine Martian climate models. Because CO₂ frost accumulates only under particular conditions of temperature, pressure, and slope orientation, mapping these gullies could reveal microclimates across the Martian surface.
“Combined with the existing observations of the geographically limited occurrence of linear dune channels and their season-sensitive activity, this sheds light on how specific (micro)climatic conditions, topography, surface characteristics, and the atmosphere interact to form unique planetary landforms,” researchers conclude.
Moreover, the study’s implications reach beyond the Red Planet. By uncovering how simple physical forces can mimic the traces once attributed to water, and perhaps even life, scientists are reminded that planetary processes often defy Earthly expectations.
Researchers say that by exploring these alien landscapes, we are expanding our understanding of how worlds, including our own, take shape and evolve.
“Mars is our nearest neighbor. It is the only rocky planet close to the ‘green zone’ of our solar system. This zone lies exactly far enough from the Sun to make the presence of liquid water possible, which is a prerequisite for life,” Dr. Roelof said. “Questions about the origin of life, and possible extra-terrestrial life, could therefore be solved here.”.
“Also, conducting research into the formation of landscape structures of other planets is a way of stepping outside the frameworks used to think about the Earth,” Roelof added. “This allows you to pose slightly different questions, which in turn can deliver new insights for processes here on our planet.”
Tim McMillan is a retired law enforcement executive, investigative reporter and co-founder of The Debrief. His writing typically focuses on defense, national security, the Intelligence Community and topics related to psychology. You can follow Tim on Twitter: @LtTimMcMillan. Tim can be reached by email: tim@thedebrief.org or through encrypted email: LtTimMcMillan@protonmail.com
