To understand the potential applicability of the process of ‘slush flow’ (a sediment-carrying flow with water and ice) to gullies on Mars, we undertook a series of flume experiments at Earth surface temperatures and pressures, which we subsequently scaled for Mars. Experiments were conducted in a 3 × 0.5 m hinged flume filled with medium-grain-size sand. The experiments were performed over a slope angle range of 10°–30°, corresponding to the slope range for gullies observed on Mars. A water ice mix, or ‘slush’, was flowed through a 19 mm-diameter silicone hose and released onto the surface at the top of the slope. A variety of morphometric parameters were measured on each form produced in the flume. The forms produced in our experiments developed the three principal morphological components of Martian gullies: alcove, channel and apron, and had a diversity of planimetric forms. The forms produced during simulations compared well to slush flows in terrestrial arctic climates, and open up the possibility that some Martian gullies may result from slush flows associated with the thawing of permafrost-active layers or surface frost under favourable thermal regimes.

Supplementary material: A complete spreadsheet of all measurements summarized in Figures 5 and 6 is available at https://doi.org/10.6084/m9.figshare.c.3930613