The European Space Agency (ESA) and its member countries began talking about a mission to Mars ever since the Russian Mars '96 mission failed. That spacecraft carried several European instruments, and the loss to European planetary science was devastating. Mars Express was conceived as a low-cost way to refly those experiments and also carry a lander communications relay which would support missions from 2003 onward.

Mars Express successfully entered orbit of Mars on December 25, 2003. It has performed excellently since then, and is in the process of carrying out its primary mission. In early 2004, the science team for Mars Express confirmed that the spacecraft had detected evidence of water ice all throughout the southern polar cap. Mars Express has also returned a stream of tantalizing images of Vallis Marineris, and other planetary features of Mars.

The experiments lost on Mars '96 and now reflown on Mars Express are significantly advancing the understanding of Mars. Mars Express will study the atmosphere and surface for a full Martian year or 687 days with seven high-resolution instruments.

For surface study, Mars Express carries four instruments. A High Resolution Stereo Camera (HRSC) will make possible topographic maps of Mars & can capture images up to a 12 meter resolution. An IR Mapping Spectrometer (aka OMEGA) conducts rock & soil analyses in the infrared spectrum. A Radio Science Experiment (RSE) measures Mars's interior composition and geodesy. A Sub-surface Sounding Radar / Altimeter (SSRA) is measuring the depth and composition of the Martian regolith.

To study the atmosphere, Mars Express carries three instruments. An Energetic Neutral Atoms Analyser (or ASPERA) studies the upper atmosphere and examines the effects of the solar wind on it. A Planetary Fourier Spectrometer (PFS) studies the atmosphere in infra-red, enabling 3D charts of temperature & pressure to be produced. A UV Atmospheric Spectrometer (aka SPICAM) measures the atmospheric composition and structure.

Mars Express will likely produce many more discoveries during its mission.