An unknown source may be producing methane close to NASA’s Curiosity rover, with potential implications for life on Mars.
Since Curiosity landed in Gale crater on Mars in 2012, it has used an instrument called the Tunable Laser Spectrometer (TLS) to measure the amount of methane in its vicinity. Alongside a background level of about 0.41 parts per billion, on six occasions Curiosity has witnessed methane spikes, where methane levels have risen to 10 parts per billion, for unknown reasons.
at the California Institute of Technology and his colleagues modelled these spikes to try to work out where they were coming from. Taking into account factors such as the local wind speed and direction at the time a spike was detected, they were able to pinpoint a possible source a few dozen kilometres away from Curiosity inside the 150-kilometre-wide Gale crater.
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“[The results] point to an active emission region to the west and the southwest of the Curiosity rover on the northwestern crater floor,” the team writes in its paper. “This may invoke a coincidence that we selected a landing site for Curiosity that is located next to an active methane emission site.”
If correct, this would be the most accurate localisation of a methane source ever on Mars. “This would make this site interesting to visit, or other similar sites that could have the same properties,” says , the project scientist for the European Space Agency’s Trace Gas Orbiter (TGO), which is currently orbiting Mars.
Although Curiosity has detected methane at the surface, the TGO has found nothing in the atmosphere. The reason for this is unclear, and is perhaps linked to Curiosity when the Martian atmosphere is calmer. But another possibility is that Curiosity just happens to sit very near to a methane source.
at York University in Toronto, Canada, says it is possible this source is some sort of crack or “seep” in the surface, leaking methane from underground, but it could be hard to locate. “It’s a bit of a haystack,” he says. “It could be covered by dust and be almost impossible to find.”
Finding the source of methane on Mars could play an important role in working out its origin. On Earth, “probably 95 per cent of methane is of biological origin”, says Svedhem, and scientists have wondered if the same might be true on Mars, perhaps indicating the presence of some form of microbial life. “Our hope was that we could see sufficient amounts of it and determine if it is a biological or not biological origin,” says Svedhem.
We aren’t yet any closer to that yet, but with methane on Mars expected to have a detectable lifespan of no more than 300 years or so, its continued presence on Mars “indicates that something is producing methane today”, says Moores. It is possible the source is geological, connected perhaps to asteroids or comets hitting Mars, but the prospect of a biological origin remains a possibility.
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