Original title: Properties of Seasonal Ice at Sisyphi Cavi and Implications for Current Modification of Martian Gullies
Apolline Leclef, Mathieu Vincendon, Cateline Lantz, François Andrieu +6 · September 2026
Scientists want to know what shapes gullies, or deep ravines, on Mars today. These ravines might form from flowing liquid water or from frozen carbon dioxide ice. To test these ideas, researchers studied an active ravine site called Sisyphi Cavi using infrared data from orbit. They tracked how surface frost changes across the seasons. Liquid water needs melting water ice, but the team found no separate water ice deposits, even in late spring when frost vanishes. Faint traces of sulfate salts also showed no direct link to the gullies. Instead, the ground is covered by see-through carbon dioxide ice. Gas geysersExplosive releases of gas from beneath CO2 ice, creating dark spots on the surface. break through this ice, leaving dark spots, but these happen in late winter and early spring. The gullies change later, in mid to late spring. Because of this timing mismatch, geysers do not seem to cause the changes. Instead, dry carbon dioxide ice avalanches or fluidizationA process where solid particles behave like a fluid due to gas flow, causing material to flow. likely drive them.
Imagine scraping ice from your car windshield on a winter morning. You might see streaks and assume they're from melting water dripping down, but sometimes the ice itself crumbles and slides off in chunks, carrying dirt with it. The hard part is that the streaks look similar whether they come from water or from ice crumbling, so you need to check the timing and conditions closely. In this paper, the streaks on Mars – gullies – were thought to come from liquid water or CO2 explosions, but the timing shows it's more likely the ice crumbling and sliding, a process similar to how windshield ice can drag debris without water.
This matters because it changes how scientists interpret active processes on Mars today. If gullies form without liquid water, it affects what we think about the planet's climate and potential for past or present habitability.
The study is limited to one site, Sisyphi Cavi, which is outside the typical latitude range of gullies, so findings may not apply to other locations. The link to fluidization or avalanche processes is suggested but not directly confirmed by the data. Only infrared observations are used, without ground truth.
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Properties of Seasonal Ice at Sisyphi Cavi and Implications for Current Modification of Martian Gullies — Apolline Leclef, Mathieu Vincendon, Cateline Lantz et al.
Abstract licence: CC0
Explanation generated by Synthesis from the abstract — it is not the original paper. This is a preprint, so it hasn't necessarily been peer reviewed.