Mars Gullies Shaped by CO2 Frost Rather Than Liquid Water

• Martian gullies, previously thought to be formed by liquid water, are likely caused by a process involving CO2 frost fluidization.
• Researchers from Université Paris-Saclay analyzed data from the Mars Express and Mars Reconnaissance Orbiter (MRO) focusing on the Sisyphi Cavi region.

Disproving Previous Theories

• Liquid water theory: Spectral analysis of the site showed a complete absence of the characteristic 1.5-micron absorption band required for liquid water during the spring thaw.
• Geyser mechanism theory: While Kieffer geysers create dark spots on the Martian surface, their activity peaks in late winter and early spring, whereas gully formation occurs later in the season.

The Air Hockey Effect

• The study proposes that subsurface CO2 sublimation creates a gaseous layer beneath ice sheets.
• This gas acts as a lubricant, allowing piles of dry ice and soil to slide down slopes, effectively carving deep trenches and alluvial-style aprons.
• This mechanism demonstrates how geological features similar to those on Earth can be created through entirely different physical processes on other planets.