Mars’ mysterious dune gullies may be the work of exploding ice blocks, say scientists

Gullies on a Martian dune inside Russell Crater show how descending ice blocks built up levees along their path. (Image: HiRISE (PSP_001440_1255_RED), NASA/JPL/University of Arizona)

Could the Red Planet’s strange dunes reveal secrets of its past? A new study suggests that Mars’ mysterious gullies may not be carved by water but by exploding blocks of dry ice. Earth scientist Dr Lonneke Roelofs from Utrecht University recreated these Martian formations in her laboratory, uncovering a process that offers a glimpse into the planet’s unique landscape. The findings appear in Geophysical Research Letters.

For years, scientists believed carbon dioxide ice might play a role in shaping Mars’ surface. However, no one had ever observed this process in action. Roelofs decided to test the theory in a controlled setting. She and master’s student Simone Visschers travelled to The Open University in Milton Keynes, which houses a ‘Mars chamber’ capable of mimicking Martian conditions.

Supported by the British Society of Geomorphology, the team simulated dune slopes under low pressure and freezing temperatures. They released CO₂ ice blocks from the top of artificial slopes and observed their movement. “After finding the right angle, we finally saw results,” Roelofs said. “The ice began to dig into the slope like a burrowing mole or the sandworms in Dune. It looked very strange.”

During the Martian winter, temperatures drop to around minus 120 degrees Celsius. Thick layers of CO₂ ice form across the dunes. As spring arrives, sunlight warms the sand beneath the ice. The trapped CO₂ rapidly turns to gas through sublimation, causing pressure to build and the ice to burst.

“In our simulation, high gas pressure blasted sand in all directions,” Roelofs said. The ice block then dug deeper into the slope before sliding down, leaving behind long trenches with ridges on each side. These lab-made gullies closely matched those seen on Mars.

Roelofs studies how natural forces shape Martian landscapes. Her earlier work showed that sublimating ice could trigger debris flows along crater walls. This new research reveals a second process—one that sculpts gullies without the need for liquid water.

“Mars is our nearest neighbour and close to the solar system’s ‘green zone’, where liquid water could exist,” she said. “Understanding its landscape helps us ask new questions about life and planetary evolution.”

The research not only explains how Mars’ dunes change with the seasons but also reminds scientists how alien environments can reshape what we know about planetary geology — and perhaps, about life itself.