Dust Complex onboard the ExoMars-2018 lander for investigations of Martian dust dynamics

International audienceThe load of suspended dust in the Martian atmosphere varies dramatically but never drops entirely to zero. Effects of airborne dust contribute to the dynamic and thermodynamic evolution of the atmosphere and its large-scale circulation processes on diurnal, seasonal and annual time-scales. Suspended dust plays a key role in determining the present climate of Mars and probably influenced the past climatic conditions and surface evolution. Atmosphere dust and windblown dust are responsible for erosion, redistribution of dust on the surface, and surface weathering. The mechanisms for dust entrainment in the atmosphere are not completely understood, as the current data available so far do not allow us to identify the efficiency of the various processes. Dust-grain transport on the surface of Mars has never been directly measured despite great interest in and high scientific and technological ramifications of the associated phenomena. This paper describes planned, future investigations of the Martian dust environment made possible by the proposed scientific payload “Dust Complex” (DC) of the ExoMars-2018 mission’s landing platform. DC is a suite of four sensors devoted to the study of Aeolian processes on Mars with a primary aim of monitoring the diurnal, seasonal, and annual dust-environment cycles by Martian-ground-based measurements of dust flux in situ, i.e., in the near-surface atmosphere of Mars. This suite includes 1) an Impact Sensor, for the measurement of the sand-grain dynamics and electrostatics, 2) a particle-counter sensor, MicroMED, for the measurement of airborne dust size distribution and number density, 3) an Electric Probe, for the measurement of the ambient electric field, and 4) a radiofrequency antenna. Besides outlining design details of DC and the characterisation of its capabilities, this presentation reviews various dust effects and dust phenomena that are anticipated to occur in the near-surface environment on Mars and that are possible to observe with DC. The negative consequences of these effects and phenomena may limit the ExoMars-2018 mission and future human development of Mars. Mechanisms associated with the influence of dust in atmosphere processes are discussed. Scientific outcomes of DC have future meteorological and environmental applications on Mars, for example, for the study of the evolution dynamics of the atmospheric aerosols and near-ground stratification. The primary objective of DC is to provide direct measurements of atmosphere aerosols parameters not attainable by other techniques. The following goals have secondary priority: ·Measurement of the daily and seasonally variability and dynamic of the atmosphere dust; ·Detection of the windblown particles and their parameters such as mass distribution and possible charge appearance; ·Measurement of the electrostatic field, electric conductivity of the Martian near surface environment and its correlation with the dust turbidity; ·Detection of micro discharges and electric perturbations in the radio frequency range