Blocks of dry ice carve gullies on Martian dunes through explosive sublimation

Blocks of dry ice carve gullies on Martian dunes through explosive sublimation
by Robert Schreiber
Berlin, Germany (SPX) Oct 15, 2025

Mysterious gullies carved into Martian sand dunes have long puzzled planetary scientists. Now, new experiments by Utrecht University Earth scientist Dr Lonneke Roelofs suggest they were dug not by flowing water or lifeforms, but by sliding blocks of solid carbon dioxide that explode and burrow as they sublimate under Martian conditions.

Roelofs replicated the process in a controlled "Mars chamber" at The Open University in Milton Keynes, which simulates the Red Planet's low pressure and extreme cold. There, blocks of CO2 ice slid down simulated dunes, carving deep, sinuous channels resembling those seen on Mars. "It felt like I was watching the sandworms in the film Dune," she said.

On Mars, CO2 ice accumulates on dunes during the frigid winter, when temperatures drop to minus 120 degrees Celsius. As spring sunlight warms the surface, ice blocks up to a meter long break away. The warmer sand beneath them causes the lower surface of the ice to vaporize instantly, producing bursts of high-pressure gas. "In our simulation, I saw how this high gas pressure blasts away the sand around the block in all directions," Roelofs explained. The escaping gas forces the block downward and forward, creating a trough surrounded by small ridges of displaced sand.

The process continues as the ice keeps sublimating, pushing the block downhill and forming a long gully flanked by rippled ridges. These features match those captured by orbiting spacecraft across Martian dune fields, confirming that CO2-driven motion can sculpt the planet's surface without the involvement of liquid water.

Roelofs previously studied how CO2 sublimation drives debris flows on Martian crater walls, but the newly identified dune gullies displayed a distinctly different morphology. To uncover the mechanism, she and master's student Simone Visschers varied the steepness of simulated slopes inside the Mars chamber until the ice blocks began to self-propel and burrow downward "like a mole or the sandworms from Dune," Roelofs recalled.

According to her findings, the blocks form when a thick layer - sometimes up to 70 centimeters - of CO2 frost builds up across southern Martian dune fields each winter. When sunlight returns, the upper layers vaporize first, leaving isolated slabs that eventually fracture and tumble downslope. As they slide, sublimation continues until the ice fully evaporates, leaving behind hollowed-out troughs and gullies at the dune base.

"Mars is our nearest neighbor and the only rocky planet close to the green zone where liquid water might exist," Roelofs said. "By studying how its landscapes form, we can think differently about similar processes on Earth and perhaps gain new insights into our own planet's evolution."

Research Report:Sliding and burrowing blocks of CO2 create sinuous "linear dune gullies" on Martian dunes by explosive sublimation-induced particle transport