Mars Express and ExoMars TGO probe Mars’s atmosphere

To study Mars’s atmosphere, ESA’s two Mars orbiters make use of a technique called ‘radio occultation’.

Mars Express beams a radio signal towards ExoMars TGO, as it is about to ‘set’ behind Mars. The radio signal travels through Mars’s upper atmosphere, causing it to bend (refract). By measuring how much the signal bends, we discover what makes up the different layers of atmosphere.

Find out more about radio occultation at the Red Planet.