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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.