An Insolation Activated Dust Layer on Mars

TL;DR

This study investigates how insolation-driven gas flow in Mars' soil creates a dust layer that reduces the wind speed needed for dust movement, with laboratory experiments quantifying the layer's thickness.

Contribution

The paper provides the first laboratory measurements of the depth of the insolation-activated dust layer on Mars and estimates its effect on saltation threshold wind speeds.

Findings

Active layer depth of 100-200 μm measured in lab.

Activation reduces saltation threshold wind speed by about 10%.

Laboratory results scaled to Martian conditions.

Abstract

The illuminated dusty surface of Mars acts like a gas pump. It is driven by thermal creep at low pressure within the soil. In the top soil layer this gas flow has to be sustained by a pressure gradient. This is equivalent to a lifting force on the dust grains. The top layer is therefore under tension which reduces the threshold wind speed for saltation. We carried out laboratory experiments to quantify the thickness of this activated layer. We use basalt with an average particle size of 67 $\mu$m. We find a depth of the active layer of 100 to 200 $\rm \mu m$. Scaled to Mars the activation will reduce threshold wind speeds for saltation by about 10%.