Saltation under Martian Gravity and its Influence on the Global Dust Distribution

Abstract

Dust and sand motion are a common sight on Mars. Understanding the interaction of atmosphere and Martian soil is fundamental to describe the planet's weather, climate and surface morphology. We set up a wind tunnel to study the lift of a mixture between very fine sand and dust in a Mars simulant soil. The experiments were carried out under Martian gravity in a parabolic flight. The reduced gravity was provided by a centrifuge under external microgravity. The onset of saltation was measured for a fluid threshold shear velocity of 0.82$\pm$0.04 m/s. This is considerably lower than found under Earth gravity. In addition to a reduction in weight, this low threshold can be attributed to gravity dependent cohesive forces within the sand bed, which drop by 2/3 under Martian gravity. The new threshold for saltation leads to a simulation of the annual dust cycle with a Mars GCM that is in agreement with observations.

References in corpus (2)

• A scaling law for aeolian dunes on Mars, Venus, Earth, and for subaqueous ripples
• Difference in the wind speeds required for initiation versus continuation of sand transport on Mars: Implications for dunes and dust storms

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• Ejected Particles after Impact Splash on Mars: Aggregates and Aerodynamics
• Experiments on Settling of Granular and Cohesive Material in Low Gravity