Mars Express was successfully launched at 17:45:46 UT on 2 June 2003 by a Soyuz FG-Fregat launcher. The Fregat upper stage then boosted the probe, consisting in a 1223-kg orbiter carrying the 71-kg Beagle 2 lander, onto a solar orbit toward Mars.

Mars Express entered orbit around Mars on 25 December 2003.

Carrying seven experiments, the orbiter will conduct a one-martian-year survey of the planet, providing an unprecedented high-resolution and mineralogical mapping. It will also conduct a search for underground waters using a radar able to identify subsurface structures up to 2 km deep. Moreover, a set of payloads will probe the atmosphere, map its composition and determine its circulation as well as its interaction with the solar wind.

Europe's first own planetary mission, Mars Express was approved in 1997 as ESA's first 'flexible' science mission. Development was delegated to industry, with Astrium appointed as prime contractor in 1998.