Contradicting claims by other projects, no methane at all has been detected in the atmosphere of Mars by the ExoMars TGO, which has been looking for it for a year now.
ABC takes up the story:
For an odourless gas, the presence — or not — of methane on Mars has created a big stink.
The newest probe to orbit Mars — the ExoMars Trace Gas Orbiter (TGO) — failed to find any methane in the Red Planet’s atmosphere, according to a paper published today in the journal Nature.
But the gas has been detected several times in the Red Planet’s atmosphere by spacecraft and rovers since 2004.
Just last week, scientists published data that confirmed the 2013 detection of methane by NASA’s Curiosity rover as it trundled across the surface of Mars.
Along with detecting two spikes in methane, the Curiosity rover found low background levels of 0.4 parts per billion of the gas, which rose in the summer months.
These results split the planetary science community, with some suggesting the methane may have come from Curiosity itself — a claim NASA rejected.
….“The TGO instruments do not see any background methane,” Dr Vandaele said.
The TGO’s optimal methane detection range is 15 to 25km above the surface, but it could pick up as little as 0.012 parts per billion at 3km altitude.
“Although none go down right to the surface, we went very close.”
….Dr Vandaele said any gas emitted should be spread evenly around Mars before being destroyed, so it should be detectable in “background” methane levels.
If the levels seen by Curiosity were correct, the TGO team argued, there must be some as-yet-unknown process that quickly removes methane from the lower atmosphere or stops it mixing with the atmosphere above.