A mysterious signal is being sent by ESA’s ExoMars Trace Gas Orbiter on 24 May, a spacecraft orbiting the Red Planet looking for evidence of possible biological or geological activity.

As part of the global 'A Sign In Space' art project, it will strike huge antennas dotted around the globe; the Green Bank Telescope (West Virginia), the Medicina Radio Astronomical Station (Italy) and the Allen Telescope Array (California).

Early tests were conducted to ensure the feasibility of the endeavour and allow the ground-based observatories to fine tune their systems to be ready for the public event.

During preparations for sending the ‘alien’ message, the Flight Control Team prepared their own special message – a picture of the team beamed down on 14 March, TGO’s 7th launch anniversary

The message was first sent up to the spacecraft from ESA’s mission control centre in Darmstadt, Germany, on 10 May. It was stored onto its memory, converted into ‘telemetry’ (data) and will this evening be beamed back down to Earth.