The puzzle of methane on Mars has deepened, and it is not looking good for the prospect of finding life. New measurements show that, whatever the source of the methane is, it is producing it 600 times faster than had been assumed and must also be trapped at a similar rate according to new research published in the 6 August issue of Nature.

Methane was first discovered in three localised regions in the atmosphere of the red planet by the European Space Agency's Mars Express probe in 2003. On Earth methane is produced by a variety of processes, including geological activity and, of course, life. Naturally, this raised the prospect that some biological activity could be creating the methane on Mars. Because methane is only stable in the atmosphere for around 300 years before it is broken down, it must mean that it has been created relatively recently in an ongoing process. However, in 2006 astronomers were surprised to find that the methane had almost entirely vanished. In the space of three years all that methane had been gobbled up, preventing it from spreading across the planet.

“Something is removing the methane from the atmosphere 600 times faster than the models can account for,” says one of the authors of the new research, Frank Lefevre of the Universite Pierre et Marie Curie, Paris. “Consequently, the source must be 600 times more intense than originally assumed, which is considerable even by Earth’s geological standards. We thought we understood how methane behaved on Mars, but if the measurements are correct then we must be missing something big.”

The new report speculates that dust on the surface of the planet may be sequestrating the methane, trapping it. Alternatively it could be that there are highly reactive chemicals such as hydrogen peroxide that are capable of destroying methane. If it is the latter, then the surface must be much more hostile to carbon-based molecules – the basics of life – than we realised.

If life is ruled out, then perhaps the oxidisation of rocks underground by running water in the here and now on Mars is producing the methane. Alternatively, the methane may have been trapped underground for billions of years and is slowly leaking out. Either way, Lefevre and his colleagues have not worried about this. “We have tackled the problem as atmospheric physicists, without worrying about the nature of the source of the methane.”

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