ExoMars Trace Gas Orbiter Instruments
Investigating the Martian atmosphere
The ExoMars Trace Gas Orbiter is an ESA and Roscosmos mission to Mars to be launched in 2016. It will investigate trace gases - gases which are present in small concentrations in the atmosphere, making up less than 1 per cent of it. There will be particular focus on hydrocarbons or sulphur species which could be signatures of active biological or geological processes, at present or in the past.
The Trace Gas Orbiter will accommodate scientific instruments for the detection of trace gases with an improved accuracy of three orders of magnitude compared to previous measurements from orbit and ground-based measurements. It will also provide new data for the study of the temporal and spatial evolution of trace gases in the Martian atmosphere, and for the location of their source regions.
The scientific payload operations of the Orbiter will start in 2017 and are planned to last for a minimum of one Martian year (687 Earth days).
The Orbiter will be used to investigate trace gases with the following scientific objectives:
Deliver a detailed characterisation of the Martian atmosphere's composition.
The first scientific goal will be to detect a broad suite of atmospheric trace gases, and key isotopologues (molecules that have at least one atom with a different number of neutrons than the parent chemical species), to establish the atmospheric inventory.
Following a positive detection of key species, geographical (location and altitude) and seasonal mapping will be carried out. Mapping of the Deuterium/Hydrogen ratio will also be performed, in order to provide new information on water reservoirs and atmospheric escape.
A third goal is characterising the state of the atmosphere, in particular temperatures, aerosols, water vapour, and ozone. The data assimilation technique adopted by the science team will allow them to model the atmospheric circulation. This will help determine whether particular gases are emanating from specific areas on Mars and to provide insights into the nature of the trace gas source.
Imaging of surface features
Another important objective is to image and to characterise features on the Martian surface which may be related to trace gas sources. The data should provide information on the geological and dynamical context (like volcanism) for any sources detected.
Mapping of subsurface hydrogen
The final objective is to map the subsurface hydrogen to a depth of one metre, with a resolution ten times better than previous measurements.
Instruments in brief
The Trace Gas Orbiter, manufactured in Europe, will carry a science payload of four instruments: