Europe’s Trace Gas Orbiter achieves operational orbit around Mars

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After a year of aerobraking to lower its orbit, the European Space Agency’s Trace Gas Orbiter has reached its planned orbit around Mars, and is about to begin studying the red planet’s atmosphere.

The primary goal is to take a detailed inventory of trace gases – those that make up less than 1% of the total volume of the planet’s atmosphere. In particular, the orbiter will seek evidence of methane and other gases that could be signatures of active biological or geological activity.

On Earth, living organisms release much of the planet’s methane. It is also the main component of naturally occurring hydrocarbon gas reservoirs, and a contribution is also provided by volcanic and hydrothermal activity. Methane on Mars is expected to have a rather short lifetime – around 400 years – because it is broken down by ultraviolet light from the Sun. It also reacts with other species in the atmosphere, and is subject to mixing and dispersal by winds. That means, if it is detected today, it was likely created or released from an ancient reservoir relatively recently. Previous possible detections of methane by ESA’s Mars Express and more recently by NASA’s Curiosity rover have been hinted at, but are still the subject of much debate.

The Trace Gas Orbiter can detect and analyse methane and other trace gases even in extremely low concentrations, with an improved accuracy of three orders of magnitude over previous measurements. It will also be able to help distinguish between the different possible origins. [emphasis mine]

The highlighted sentence is important. Pinpointing a region where methane is concentrated will allow scientists to better understand where it is coming from, and what is causing its release. It could be microbiological life, but it also could be from active volcanic processes. Finding either or both would be significant, to put it mildly.



  • Localfluff

    It took a year for this ExoMars orbiter to aerobrake itself into science orbit. ESA tried out aerobraking at Venus with Venus Express. I would have hoped for this to have had greater potential.

  • Tom D

    I understand that Mars’s extremely thin atmosphere is quite variable in density and height. Aerobraking at Mars is much less useful and much riskier than aerobrake at Earth (or Venus). I am not surprised that they were very cautious about this maneuver.

  • Localfluff

    @Tom D
    Aerobraking actually happens at very high altitude where the atmosphere is very thin. So thin that there are no aerodynamics, just an average of particles hitting the spacecraft’s profile as it goes through the very thin gas of the exosphere. Aerobraking is as effective at Earth as at Venus or Mars. One just chooses the appropriate altitude and thus air density. Why this exomars orbiter has taken so long, I don’t know. I’ll probably look into it once it starts doing science. I suspect that the guys involved don’t mind ensuring themselves longer employments on the project and that it is therefor little opinion against delaying stuff.

    It has even been suggested that a spacecraft could aerobrake at Pluto. A planet with no real atmosphere, but the exosphere, the particles leaving the surface without really hitting each other, could be enough to help a probe enter orbit.

  • Edward

    I’m with Tom D on this one. After the loss of Mars Climate Orbiter in 1999, NASA may be a little more cautious for a while.

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