Plasma-Dust System in the Martian Ionosphere

We present a theoretical model describing possible mechanism of formation and evolution of plasma-dust clouds observed in the Martian ionosphere by the Mars Science Laboratory Curiosity rover in March 2021. The model describes sedimentation of dust particles in the supersaturated carbon dioxide vapor, growth of dust seeds due to carbon dioxide nucleation, charging of dust particles, and changes in electron and ion number densities of the ionospheric plasma over time in particular. It is demonstrated that formation of the layered structure of the dust cloud the characteristic sedimentation time of which is on the order of several minutes can be illustrated within the framework of the proposed model. Characteristic size of the dust particles are calculated and found to be consistent with the results of the measurements. In addition, characteristic charges of dust particles in the presence and in the absence of the photoelectric effect are calculated. It is demonstrated that dust particles acquire negative charge in the absence of the photoelectric effect. Simultaneously, number densities of plasma electrons and ions decrease. In the presence of the photoelectric effect, particles containing metallic impurities carry a positive charge. In the process, number density of plasma electrons increases, while ion number density continues to decrease.