This transmission is the fourth in a series of five ESA TV Exchanges on Mars Express, ESA's first mission to another planet. It looks at what the mission hopes to discover on and below the surface of Mars, the instruments it will use and what the already know about surface composition form previous studies. In particular, the transimission covers three instruments: Omega, Marsis and the HRSC. The programme comprises of a 7 minute A-roll with split audio (english commentary/international sound) and is complimented by a 20-minute B-roll with clean international sound.