Laboratory Experiments on Electrostatic Discharging in Martian Dust Devils and Dust Storms

Due to the prevalence of Martian dust devils and dust storms, an understanding of the underlying physics of electrical discharges occurring in Martian dust is critical to future Mars exploratory missions. When dust particles come into contact, charge can be transferred between the grains. Wind driven dust studies (Weather, 1969) show that in the case of particles with identical compositions, the particle with the larger radius in a collision preferentially becomes positively charged. The stratification of particle sizes generated by upwinds within a dust cloud causes an electric dipole to form. When the electric potential within the cloud exceeds the breakdown voltage of the surrounding atmosphere, a discharge occurs. Mars' low atmospheric pressure and arid, windy environment suggest that the dust near the surface of Mars is even more susceptible to triboelectric charging than terrestrial dust. Electrical discharges on Mars should occur more frequently but at lower intensities than those seen on Earth. We have conducted laboratory experiments to examine the creation of discharges due to horizontal mixing and vertical charge separation in a simulated Martian environment. The range of pressures and the amount of mass loading required to produce these discharges have been examined. Measurements done in our lab on the charging of single dust grains show that particles of JSC-Mars-1, a Martian regolith simulant, can have large electrical potentials due to triboelectric charging. When JSC-Mars-1 is stirred or vertically dropped in a low-pressure CO₂ atmosphere, electrical discharges are both visually and electronically detected. Measurements of the frequency and intensity of these discharges show that they can occur under conditions expected on the Martian surface. This work is supported by NASA Space Science GSRP, NGT5-50345.