The Mars atmosphere
Today, Mars is characterized by his extreme thin, dry, and cold, atmosphere, that mainly consists of Carbon dioxide. Changes in the solar insolation lead to pronounced diurnal changes in the atmosphere due to the very low surface pressure of just 4 mbar. Furthermore, Mars has no oceans like the Earth that could buffer these temperature fluctuations. A significant part of the atmospheric carbon dioxide (~30%) condenses over the polar caps in the winter hemispheres of Mars due to the very low temperatures in the polar night und sublimates in the following spring.
From time to time, the whole planet is shrouded by global dust storms, induced by the high atmospheric variability and the low atmospheric pressure. These dust storms lead to significant changes in the global climate of Mars.
Radio sounding experiments in the microwave range are able to provide atmopheric profiles of the neutral atmosphere of Mars at the very high vertical resolution. They cover the altitude range a few hundred metres above the surface up to an altitude of about 40 km. This high vertical resolution makes it possible to study not only the free troposphere but even the planetary boundary layer and its vertical extent [Hinson et al., 2008]. Even small scale atmospheric phenomena can be investigated [Tellmann et al., 2013]. The extensive data set of the Mars Express Radio Science Express (MaRS) allows to draw conclusions about global atmospheric phenomena like zonal winds or global stationary waves [Tellmann et al., 2013], despite the limited global coverage of radio occultation experiments.