ExoMars 2016 FAQs

Methanogens are believed to have evolved on Earth several billion years ago, before the Earth built up oxygen in its atmosphere. Since Mars has never had an oxygenated atmosphere, methane in its atmosphere could betray the existence of life similar to Archaea that developed when Mars was warmer and wetter.

However, methane is also released on the Earth by naturally occurringhydrocarbongas reservoirs, and a contribution is also provided by volcanic and hydrothermal activity. Distinguishing between these potential processes on Mars is a priority for TGO.

In more detail, methane on Mars is destroyed by ultraviolet light from the Sun and expected to have a short lifetime of around 400 years. Also, atmospheric mixing should quickly lead to a more or less uniform background concentration. But previous measurements by ESA’s Mars Express mission and ground-based observatories hint at seasonal variations in methane abundance, with concentrations varying with location and time. Therefore, on one hand there must be active sources of methane to replenish the supply and on the other, there must a relatively quick way of removing it in order to account for the apparent variations in the measurements. Understanding the processes at play is a goal of the Trace Gas Orbiter mission.

Methane can also be produced by non-biological reactions between water and a mineral called olivine (a process called ‘serpentinisation’). On Mars, this may occur underground, perhaps in combination with warmer, volcanic environments.

Methane is broken down over time by ultraviolet radiation, oxidising it through chemical reactions into carbon dioxide, the primary ingredient of the martian atmosphere. In addition, winds on Mars can redistribute the methane from its original source, reducing localised concentrations.

Delays ensued and the plans changed. In 2009, a cooperative agreement between NASA and ESA was signed, stating that the two agencies would undertake further robotic Mars exploration together. The design of the first mission was altered from the original ESA plans. It became a European-built orbiter tasked with the detection and mapping of trace gases in the martian atmosphere, and a landing demonstrator module, aimed to demonstrate the European technology needed for successful Mars landing. The mission would be launched in 2016, serving as a data relay for future surface missions.

The European rover and a similarly-sized US rover would then be landed two years later using NASA’s Skycrane system, as successfully used to deploy the Curiosity rover on Mars in 2012. This was found to be too challenging and rather a single large, Curiosity rover-like concept was envisaged, accommodating the European drill and payload along with US instruments.

In this scenario, NASA was to provide the launch vehicle and two of the four scientific instruments for the orbiter. However, NASA pulled out of the ExoMars programme in 2012 due to budgetary constraints.

Subsequent negotiations between ESA and Roscosmos led to an agreement for a new partnership for ExoMars. In this cooperation, Russia provides the two launch vehicles and various payload elements, with the original 2016 launch opportunity for the first mission staying intact.

In more detail, TGO will be able to detect key isotopologues of methane and water. Isotopologues are molecules in which at least one atom has a different number of neutrons than in the parent molecule: for example, HDO is an isotopologue of H2O, where on hydrogen atom has been replaced by a deuterium atom. Measurements of methane on Earth suggest that methane originating from biological and geological processes have distinctive isotopic signatures, and thus TGO’s measurements will be key in constraining the origin and history of these species on Mars.

TGO also has the capability to detect additional minor atmospheric constituents that may exist but have yet to be detected.

While TGO will search for tracers of life or geological activity from orbit, the 2022 mission will be the first to combine roving over the martian surface with drilling and sampling material from a depth of up to two metres below the surface, in order to search for evidence of past or extant life protected from the harsh radiation environment present on the planet’s surface today.

The second phase will take up to one year, and consist of hundreds of ‘aerobraking’ passes, a process that involves lowering the lowest point of the orbit (‘periares’) such that it grazes the upper atmosphere. Every time the spacecraft flies through this part of its orbit, it will be slowed down a small amount by air drag. After many hundreds of orbits doing this, it will eventually arrive in its circular science orbit 400 km above the surface.

The landing will take place during global dust storm season and its measurements will include the first made of atmospheric particle charging effects, to help understand how global dust storms get started on Mars. The Dust characterisation, Risk Assessment, and Environment Analyser on the Martian Surface (DREAMS) package will measure local wind speed and direction, humidity, pressure, and atmospheric temperature close to the surface, transparency of the atmosphere, and atmospheric electric fields.

In addition, a simple camera (DECA) will take 15 monochrome images during the descent of Schiaparelli to provide engineering insight into the landing process and to identify help the actual landing location. However, it is not designed to take images from the surface.