2016

ExoMars Trace Gas Orbiter

Numerous robotic flyby, orbiter, lander, and rover missions have been sent by the world’s space agencies to study the interesting and enigmatic history of Mars. A hallmark of this global program of Mars exploration has been that new missions follow up on previous puzzles and discoveries. In March 2016, the European Space Agency (ESA) launched the ExoMars Trace Gas Orbiter (TGO) mission, focusing its scientific studies on the detection and mapping of minor atmospheric gases (like methane) that could potentially provide diagnostic information about the past geologic and potentially biologic history of Mars. The spacecraft successfully went into an elliptical orbit in October 2016, and began using aerobraking to get to its eventual low-altitude near-polar circular orbit.

The detection and monitoring/mapping of methane on Mars has had a complicated history. Missions to the surface have measured only very small amounts—typically from zero to ten parts per billion, or ppb (Earth’s atmosphere typically has about 1,800 ppb). However, some ground-based telescopic observations have detected much higher methane levels—30 ppb or more—that vary over time on different parts of the planet. Atmospheric chemists have realized for decades that methane is relatively quickly broken down by ultraviolet radiation in the Martian atmosphere, so detection of significant amounts would imply that there is some active source that resupplies it. Potential sources include weathering of subsurface rocks, breakdown of other more complex surface or atmospheric organic molecules, or biologic activity of some kind.

While it may be a long shot, the possibility of deep, subsurface microbes or other biologic activity creating methane on Mars is a strong driver for TGO’s measurements. Planetary scientists and astrobiologists worldwide will be watching with great interest as the mission’s data sets continue to roll in and get analyzed and interpreted.

TGO also carried and deployed a small lander called Schiaparelli, designed to test ESA technologies for entry, descent, and landing vehicles to Mars, and pave the way for a more ambitious European rover mission in the early 2020s. The lander carried cameras and meteorology equipment, but, unfortunately, it crashed onto the surface because of software problems during the landing process.

Artist’s rendering of the European Space Agency’s ExoMars Trace Gas Orbiter.