Windblown Dust on Venus

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  • 1 Laboratory for Planetary Studies, Cornell University, Ithaca, N. Y. 14853
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Abstract

The threshold frictional velocity u*0 necessary to initiate grain movement on the Venus surface is 1–2 cm s−1. Particles smaller than 30 or 40 µm in effective diameter will be so moved and suspended at the threshold of movement. A small diameter turnup in u*0 is expected if there is surface cohesion. These values of u*0 require velocities >0.3 m s−1 above the surface boundary layer for grain motion on the surface. Theoretical arguments and Venera 8 Doppler measurements suggest marginally that dust should not be raised at the Venera 8 landing site (10°S), but should be raised at higher latitudes. Dust carried to tens of kilometers altitude will be transported over the entire planet and may make important contributions to the solar energy deposition, general circulation, and cloud chromophore problems. However, the Venera 8 photometer measurements and the low albedo of reasonable surface materials imply a clear lower atmosphere at 10°S, despite the fact that dust raised at high latitudes should contribute to the aerosol content at 10°S. Dust raising on Venus may be inhibited by limited vertical turbulent diffusion or by thermal sintering of particles on the planetary surface.

Abstract

The threshold frictional velocity u*0 necessary to initiate grain movement on the Venus surface is 1–2 cm s−1. Particles smaller than 30 or 40 µm in effective diameter will be so moved and suspended at the threshold of movement. A small diameter turnup in u*0 is expected if there is surface cohesion. These values of u*0 require velocities >0.3 m s−1 above the surface boundary layer for grain motion on the surface. Theoretical arguments and Venera 8 Doppler measurements suggest marginally that dust should not be raised at the Venera 8 landing site (10°S), but should be raised at higher latitudes. Dust carried to tens of kilometers altitude will be transported over the entire planet and may make important contributions to the solar energy deposition, general circulation, and cloud chromophore problems. However, the Venera 8 photometer measurements and the low albedo of reasonable surface materials imply a clear lower atmosphere at 10°S, despite the fact that dust raised at high latitudes should contribute to the aerosol content at 10°S. Dust raising on Venus may be inhibited by limited vertical turbulent diffusion or by thermal sintering of particles on the planetary surface.

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