Scientists have uncovered how blocks of frozen carbon dioxide dig eerie channels into Martian dunes through explosive sublimation. Lab experiments replicating Martian conditions revealed the process, matching observed features on the Red Planet. The discovery explains a long-standing geological puzzle without needing water or life.
For years, researchers puzzled over the origins of sinuous gullies scarring Mars' dunes, features that hinted at possible past water flows or even life. Dr. Lonneke Roelofs of Utrecht University led experiments showing that dry ice—frozen CO2—can create these formations independently. Her findings, published in Geophysical Research Letters, demonstrate a process unique to Mars' thin atmosphere and extreme temperatures.
During the Martian winter, temperatures drop to around minus 120 degrees Celsius, allowing a layer of CO2 ice up to 70 cm thick to blanket dune fields in Mars' southern hemisphere. As spring arrives, sunlight warms the slopes, causing large blocks—sometimes a meter long—to break loose from shaded dune tops. The blocks slide downhill, but the real action happens underneath: the warm sand causes the ice's base to sublimate directly into gas. This gas expands rapidly, building pressure that blasts sand away in all directions, mimicking an explosion.
"In our simulation, I saw how this high gas pressure blasts away the sand around the block in all directions," Roelofs explained. The block burrows into the slope, forming a hollow ringed by sand ridges, then continues sliding and digging, carving deep trenches that match Mars' gullies precisely. Roelofs and master student Simone Visschers conducted the tests in a Mars simulation chamber at the Open University in Milton Keynes, England, funded by the British Society of Geomorphology. They varied dune slopes until observing the ice blocks move like burrowing moles.
"It felt like I was watching the sandworms in the film Dune," Roelofs said of the eerie motion. This builds on her prior work on CO2-triggered debris flows along crater walls, but these dune gullies required a distinct mechanism. The process fully evaporates the ice at the slope's base, leaving hollows in the sand.
Roelofs highlights Mars' appeal: as the nearest rocky planet in the solar system's habitable zone, it offers clues to life's origins and fresh perspectives on planetary geology. "Mars is our nearest neighbour. It is the only rocky planet close to the 'green zone' of our solar system," she noted, emphasizing liquid water's role as a life prerequisite.