Windblown dust on Mars: laboratory simulations of flux as a function of surface roughness

Experiments were conducted to determine the flux of dust (particles <few microns in diameter) under Martian atmospheric conditions for surfaces of three aerodynamic roughnesses (z0). For smooth surfaces on Mars (z0=0.00125 cm corresponding to 0.0125 cm on Mars) suspension threshold was not achieved at the highest velocities run (u∗=322 cm/s); for a moderately rough surface (z0=0.010 cm corresponding to 0.10 cm on Mars), flux averaged 1.5×10−7 g/cm2/s; for a rough surface (z0=0.015 cm corresponding to 0.15 cm on Mars), flux averaged 5×10−7 g/cm2/s. Although the results are preliminary, flux varied widely as a function of wind speed and roughness, suggesting that raising dust into suspension on Mars is complex. Nonetheless, using these results as a guide, 9000 Mt of dust could be raised into the atmosphere of Mars per second from only 5% of the surface.