ExoMars Trace Gas Orbiter confusingly finds no methane in Mars atmosphere

Initial results from the ExoMars Trace Gas Orbiter (TGO) have found little evidence of methane on the Red Planet, a potential sign of life, despite spotting the gas on several previous occasions.

The TGO originally reached Mars in 2016 with a key goal to gain a better understanding of methane and other trace gases in its atmosphere.

Methane has previously been discovered on both the planet’s surface and in its atmosphere but the satellite found nothing.

It uses spectrometers – NOMAD and ACS – to make high-resolution “solar occultation measurements” of the atmosphere.

This looks at the ways sunlight is absorbed in the atmosphere to reveal the chemical fingerprints of its ingredients.

Methane is of particular interest for Mars scientists because it can be a sign of life as well as geological processes. On Earth, for example, 95 per cent of methane in the atmosphere comes from biological processes.

Because it can be destroyed by solar radiation on timescales of several hundred years, any detection of the molecule in present times implies it must have been released relatively recently, even if the methane itself was produced millions or billions of years ago and remained trapped in underground reservoirs until now.

Previous reports of methane in the Martian atmosphere have been intensely debated because detections have been very sporadic in time and location, and often fell at the edge of the instruments’ detection limits.

Håkan Svedhem, the European Space Agency’s project scientist for the TGO, was not downbeat about the findings.

“We are delighted with the first results from the Trace Gas Orbiter,” he said. “Our instruments are performing extremely well and even within the first few months of observation were already providing exquisite data to a much higher level than previously achieved.

“Just as the question of the presence of methane and where it might be coming from has caused so much debate, so the issue of where it is going, and how quickly it can disappear, is equally interesting.

“We don’t have all the pieces of the puzzle or see the full picture yet, but that is why we are there with TGO, making a detailed analysis of the atmosphere with the best instruments we have, to better understand how active this planet is – whether geologically or biologically.”

The spacecraft settled into orbit just months before last year’s global dust storm, which enveloped vast swathes of Mars. It monitored the storm from the moment it began and studied how the dust affected water vapour in the atmosphere.

The storm also caused the loss of Nasa’s Opportunity rover, which is assumed to have run out of power after dust collected on its solar panels.

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