Sand on Mars

Boiling Water Shapes Martian Terrain. The discovery of this exotic process radically changes our interpretation of the Martian surface, making it difficult to directly compare flows on Earth and Mars. post

On Mars where the atmosphere is much thinner than on Earth water can boil at temperatures as low as 0 °C. During the Martian summer, when the subsurface water ice begins to melt and emerge at the surface, where the mean temperature reaches 20 °C, it immediately boils.

Experiments showed that in the flows produced under terrestrial conditions the water gradually seeped into the sand leaving no trace on the surface after drying. However, what was observed in the Martian chamber was very different.

The water produced by the melting ice at low pressure started to boil as soon as it reached the surface, and the gas released caused the ejection of sand grains. These gradually formed small ridges at the front of the flow, which, as they grew larger, became unstable and actually produced avalanches of dry sand.

The process was even more violent at lower pressures. Contrary to what is observed on Earth, the surface, once dry, therefore exhibited a series of ridges.

Transport processes induced by metastable boiling water under Martian surface conditions. Massé et. al. nature

Liquid water may exist on the Martian surface today, albeit transiently and in a metastable state under the low atmospheric surface pressure.

Here, we present lab experiments in which a block of ice melts and seeps into underlying sediment, and the resulting downslope fluid propagation and sediment transport are tracked.