The Trace Gas Orbiter is the first of two missions of the ESA-Roscosmos ExoMars programme that will attempt to discover whether life has ever existed on Mars.

The spacecraft arrived at the Red Planet in October 2016 and is making a detailed inventory of the atmosphere and mapping signatures of sub-surface water. It is capable of sniffing out the composition of the trace gases such as methane and water vapour, which make up less than one percent of a planet’s atmosphere. Because of the key role natural biological processes plays in Earth’s methane production, confirming the existence of methane on Mars and distinguishing between its potential sources, is a top priority of the Trace Gas Orbiter.

In addition to its prime science mission, the orbiter also carries a sophisticated radio relay capability provided by NASA. The Electra Proximity Payload (Electra) is a telecommunications package that acts as a communications relay and navigation aid.

TGO is currently responsible for relaying approximately 60% of all data sent to Earth from Mars across all space agencies thanks to its convenient science orbit. It will also serve as data relay support for ESA's ExoMars Rover, Rosalind Franklin, which is planned to launch in 2022.

TGO delivered the Schiaparelli entry, descent and landing demonstrator, which did not survive landing after conflicting information in the onboard computer caused the descent sequence to end prematurely.