Some dune fields on Mars have parallel channels called linear dune gullies. Contrary to their name, these gullies are often very winding. It was previously believed that these features were formed as a result of mudflow processes caused by liquid water. However, new satellite image data shows that they are active in the spring as a result of a process caused by carbon dioxide ice. Ice forms on Martian dunes during the local winter and breaks off at the top of the dune in early spring. Using new laboratory experiments in the Mars chamber, planetary scientists from Utrecht University, the University of Le Mans, the University of Nantes, the Institute of Planetology and Astrophysics of Grenoble and the Open University show that linear dune gullies are formed from blocks of carbon dioxide ice that slide or burrow into the sandy slope of a dune and move down the slope, abruptly throwing out the surrounding sand. This excavation process is caused by powerful gas flows created by carbon dioxide-ice sublimation as ice turns into carbon dioxide. While the sliding of carbon ice blocks explains the formation of shallow channels, the burying of carbon ice explains the creation of deep and sinuous channels on the dunes of Mars.
Two examples of Martian dunes with linear dune gullies: (a) linear dune gullies in the Galle Crater dune field; (b) linear dune gullies in a dune field in an unnamed crater in the center of Hellas Planitia. Image credit: Roelofs etc.., doi: 10.1029/2024GL112860.
Linear dune gullies are unique and mysterious landforms that occur in dune fields in the mid-latitudes of the planet Mars.
These parallel, despite their name, often meandering channels with sharp bends, limited headwater areas, distinct levees and pitted channel ends have no terrestrial counterpart.
They are distinct from the classic gully landforms seen on steep slopes on Mars and Earth, which consist of an erosional niche, channel, and deposit and are often larger than linear dune ravines.
“In our model, we saw high gas pressure pushing sand around the block in all directions,” said Utrecht University researcher Lonneke Roelofs, lead author of the study.
“As a result, the block crashes into the slope and becomes trapped, surrounded by small ridges of settled sand.”
“However, the sublimation process continues and therefore the sand continues to splash in all directions.”
“Through this process, the block gradually moves downwards, leaving behind a long and deep ravine with small sand ridges on either side.”
“This is exactly the type of gully that is also found on the Red Planet.”
In their study, Dr. Roelofs and co-authors combined laboratory experiments in which they released clumps of carbon dioxide and ice on sandy slopes under Martian atmospheric pressure with observations of linear dune gullies on the Russell Crater megadune.
“We tried different things, modeling the dune slope at different steepness angles,”
“We let a piece of carbon dioxide ice fall from the top of the slope and watched what happened.”
“Having found the right slope, we finally saw the results. An ice block of carbon dioxide began to bite into the slope and move down, like a burrowing mole or sandworms from Dune. It looked very strange.”
“But how exactly do these ice blocks form? The carbon dioxide blocks form on desert dunes halfway to the southern hemisphere of Mars.”
“During the winter, a layer of carbon dioxide ice forms on the entire surface of the dune field, sometimes up to 70 cm thick! In the spring, this ice begins to heat up and sublimate.”
“The last remnants of this ice are located on the shaded side of the dune tops, and this is where the blocks break off when the temperature gets high enough.”
“Once the blocks reach the base of the slope and stop moving, the ice continues to sublimate until all the carbon dioxide has evaporated, leaving only a depression in the sand at the base of the dune.”
study was published on October 8 in the magazine Letters on Geophysical Research.
_____
Lonneke Roelofs etc.. 2025. Sliding and burrowing blocks of CO2 create sinuous “linear dune gullies” on Martian dunes via particle transport caused by explosive sublimation. Letters on Geophysical Research 52(19): e2024GL112860; doi: 10.1029/2024GL112860
