Sliding and Burrowing Blocks of CO2 Create Sinuous “Linear Dune Gullies” on Martian Dunes by Explosive Sublimation-Induced Particle Transport

Martian linear dune gullies are landforms consisting of parallel and often sinuous channels with distinct levees and pit-shaped endings that occur in the mid-latitudes on Mars. Recent observations link their formation to sublimating ${\text{CO}}_2$-ice blocks that slide downslope in early spring. Here we combine laboratory experiments in which we release ${\text{CO}}_2$-ice blocks on sandy slopes under Martian atmospheric pressure with observations of linear dune gullies on Russell crater mega dune to test this hypothesis. We show that, on steep slopes ($>$22.5° in our experiments) sublimating ${\text{CO}}_2$-ice blocks slide down-slope, creating straight, shallow channels with indistinct levees. On more gentle slopes (22.5° in our experiments), sublimating ${\text{CO}}_2$-ice blocks burrow themself into the sand and slowly migrate downslope by excavating their surroundings by explosive gas-driven sediment transport. The burrowing movement helps explain the formation of unique characteristics of linear dune gullies; high levees, deep channels, channel sinuosity, and pit-shaped channel endings.