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 (z(0)). For smooth surfaces on Mars (z(0) = 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 (z(0) = 0.010 cm corresponding to 0.10 cm on Mars), flux averaged 1.5 x 10(-7) g/cm(2)/s; for a rough surface (z(0) = 0.015 cm corresponding to 0.15 flux on Mars), flux averaged 5 x 10(-7) g/cm(2)/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. (C) 2000 Elsevier Science Ltd. All rights reserved.