Current understanding of the upper atmosphere, ionosphere and airglow of Mars and Venus

As stated by Chamberlain in 1961, airglow is a nonthermal radiation emitted by a planetary atmosphere. The observation of the Mars and Venus airglow (ground-based or from orbit) provided a large amount of information on the atmosphere and ionosphere of those planets. From these emissions, in the IR, visible and UV spectral range, we can learn about the composition, the energetics and the dynamics. I will describe what is the current understanding of the couple upper atmosphere/ionosphere of both planets, and especially which discoveries were made from airglow measurements. Since Mars Express is currently orbiting around the red planet, carrying onboard an infrared and ultraviolet spectrometer (SPICAM), I will take the opportunity to present the latest observations of the upper atmosphere and ionosphere of Mars. I will show that SPICAM is able to provide information on the ionosphere from the lower layers (~80 km), where the atmosphere is interaction with interplanetary dust particles, up to ~ 300 km, where the atmosphere interacts with the solar wind. The next opportunity to learn more about the Venus atmosphere and ionosphere from airglow measurements will come from the IR-UV spectrometer aboard the ESA Venus Express mission. The launch is currently scheduled on November 2005. The presentation will outline the main expectations regarding airglow measurements.