A lower-than-expected saltation threshold at Martian pressure and below

Area of Science:

• Planetary Science
• Geomorphology
• Fluid Dynamics

Background:

• Aeolian sediment transport, forming ripples and dunes, occurs on Earth and Mars.
• Terrestrial analogs and environmental simulations aid understanding of planetary geomorphological processes under unusual conditions.

Purpose of the Study:

• To investigate Martian sediment transport under simulated planetary conditions.
• To explore a previously unexamined saltation regime relevant to Mars.

Main Methods:

• Laboratory experiments using a closed-circuit wind tunnel within a vacuum chamber.
• Operation at extremely low pressures to simulate Martian atmospheric conditions.

Main Results:

• The threshold wind speed for saltation deviates from models at high grain-to-air density ratios.
• Impact ripples formed consistently across the pressure range, with stable wavelength and propagation velocity.
• Sediment transport at low Reynolds number and high density ratio appears dominated by collective grain inertia effects.

Conclusions:

• Martian aeolian processes operate in a unique saltation regime.
• Impact ripple formation is pressure-independent under simulated Martian conditions.
• Collective effects in the granular collisional layer are crucial for understanding Martian sediment transport.