Due to the prevalence of Martian dust devils and dust storms, an understanding of the underlying physics of electrical discharges in Martian dust is critical to future Mars exploratory missions. Mars' low atmospheric pressure and arid, windy climate provide an environment which supports triboelectric charging of dust. The turbulent motions of particles within a dust cloud cause individual dust particles to collide. This contact allows charge to be transferred between the grains. When the grains have identical compositions, the particle with the larger radius in the collision preferentially becomes positively charged. The upwinds within the dust cloud can then carry the lighter, negatively-charged particles to higher altitudes. The stratification of particle sizes causes an electric field to form. When the electric potential within the cloud exceeds the breakdown voltage of the surrounding atmosphere, a discharge occurs.; I have performed two laboratory experiments to examine the creation of electric fields and the subsequent discharges in a low-pressure CO 2 atmosphere. In both experiments, discharges have been visually and electronically detected, and measurements of their frequencies and intensities showed that triboelectric charging is a sufficient mechanism to promote strong electric fields. The range of pressures, horizontal wind speeds, and particle-size distributions required to efficiently produce these discharges have also been examined. These experiments demonstrate that electrical discharges can occur under conditions expected on the Martian surface.; Additionally, I have created a simple theoretical model to constrain the parameters involved in the dust charging experiments. This model supports the ideas developed in the experimental phase of this project.
展开▼
