Mars Express and MARSIS

Abstract

The Mars Express mission to be launched in 2003 will provide high resolution measurements of the Martian atmosphere and ionosphere. The neutral density, temperature, and composition will be measured, and MARSIS, a low frequency radar experiment, will probe the Martian plasma environment for electron densities in the range from 100 to 3 × 10⁵ electrons/cm^-3. The radar will for the first time make measurements of the ionosphere in the sub-solar and midnight regions which were not accessible to previous missions. The radar will provide global coverage and an increase in spatial resolution of vertical electron density profiles, which can be used to improve understanding relationships between the neutral atmosphere and ionosphere, and the interactions of the solar wind with the planet. The radar may be able to detect effects associated with magnetic merging, plasma clouds, and plasma streams, which have been predicted in the dayside/terminator ionosphere. Measurements on the nightside can be used to search for proposed fine structures (‘holes’) in the electron density. Hydrodynamic waves are predicted to be excited by the solar wind/ionosphere interaction and their influence on the electron densities can be observed with the radar. Neutral density and temperature profiles are required to understand the details of the vertical variations of the electron density. This includes testing for effects induced on the electron density profiles by dust storms and by precipitations of solar wind ions in cusp-like magnetic regions. The search for trace elements by optical spectrometers may reveal magnesium ions in predicted meteoric layer.