Some dunes on Mars are covered with meandering gullies defying what we know for gully formation here on Earth. Planetary scientist Dr. Lonneke Roelofs from Utrecht University investigated how these gullies were formed. In a test setup, she observed that blocks of CO2 ice ‘dug’ these gullies in a unique way.
Other researchers had previously suspected that these blocks could play a role in the formation of the gullies. Roelofs has now proven this by having CO2 ice blocks actually dig those gullies in an experiment – a phenomenon that we do not know here on Earth and that had never been observed by anyone before.
Ice forms on the dunes during the Martian winter when it is minus 120 degrees Celsius. At the end of winter, the dune slopes heat up and blocks of ice break off, some of which are up to a metre long. Due to the thin atmosphere and the large temperature difference between the warm dune sand and the ice, the bottom side of the ice immediately turns into gas, a process referred to as sublimation. As a kilo of gas requires far more space than the same weight of ice, the ice explodes, so to speak. “In our simulation, I saw how this high gas pressure blasts away the sand around the block in all directions”, says Roelofs. As a result, the block digs itself into the slope and becomes trapped in a hollow surrounded by small ridges of settled sand. “However, the sublimation process continues, and so the sand keeps on being blasted in all directions.” Due to this process, the block gradually moves downwards, leaving a long, deep gully with small sand ridges on either side behind it. This is exactly the type of gully that is also found on the Red Planet. The results have now been published in Geophysical Research Letters.
Video footage from the experiments – watch as the ice blocks dig in
Source & further reading: Mysterious gullies on Mars appear to have been dug, but by whom or what?
Publication: Lonneke Roelofs, Simone R. Visschers, Susan Conway et al., ‘Sliding and burrowing blocks of CO2 create sinuous “linear dune gullies” on Martian dunes by explosive sublimation-induced particle transport’, Geophysical Research Letters, https://doi.org/10.1029/2024GL112860