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

TL;DR

This study investigates how Martian gravity affects dust and sand saltation, revealing a lower threshold for particle lift that influences the planet's dust cycle and surface features.

Contribution

It provides the first experimental measurement of saltation threshold under Martian gravity, showing gravity-dependent cohesive forces significantly lower the lift threshold.

Findings

Saltation threshold under Martian gravity is 0.82 m/s.

Cohesive forces within sand drop by two-thirds under Martian gravity.

The new threshold improves dust cycle simulations matching observations.

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.