It's a God-awful smell affair.... is there life on Mars? Rocks ruled out as source of mystery methane on Red Planet

(Yes, pedants, we know natural methane is odorless. Don't get in the way of a Bowie headline)

his low-angle self-portrait of NASA's Curiosity Mars rover shows the vehicle at the site from which it reached down to drill into a rock target called "Buckskin." The MAHLI camera on Curiosity's robotic arm took multiple images on Aug. 5, 2015, that were stitched together into this selfie. Credit: NASA/JPL-Caltech/MSSS
Image credit: NASA/JPL-Caltech/MSSS

Ever since methane was detected on Mars, boffins have been trying to find out how it got there. Research published in Scientific Reports on Monday has ruled out one source – rocks being eroded by wind.

The presence of the hydrocarbon gas has excited the scientific community, since it can be produced via biological as well as non-biological processes, suggesting there may be – or once was – extraterrestrial life on the Red Planet. An international team of eggheads has rekindled that biological methane possibility after ruling out the idea that the gas is released from rocks that have been gnawed away by winds.

“Using the data available, we estimated rates of erosion on the surface of Mars and how important it could be in releasing methane,” said Jon Telling, co-author of the paper and a geochemist at Newcastle University in the UK. “And taking all that into account we found it was very unlikely to be the source.”

Scientists working at the European Space Agency and NASA both detected whiffs of methane in 2013. The largest spike showed that there was up to 15 parts per billion by volume of methane in the atmosphere. That may not sound like much, but it amounts to about 46 tonnes of methane in an area of 49,000 square kilometers (30,447 square miles), according to a previous paper published in April.

But in order for wind erosion to be a feasible explanation for all that gas, it would mean that the Martian rocks would have to be as rich in methane as some of the oil shales on Earth. The latest research, however, suggests that that’s very unlikely.

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“In fact, in a few cases, the rate of erosion is estimated to be comparable to those of cold and arid sand dune fields on Earth,” said Telling. Although the researchers have ruled out wind erosion, it doesn’t necessarily mean there are aliens on Mars either.

“What’s important about this is that it strengthens the argument that the methane must be coming from a different source. Whether or not that’s biological, we still don’t know,” he added.

Although the origins are unknown, the process that produces the gas seems to be pretty temperamental. After scientists managed to detect about 21 parts per billion units by volume - the largest reading ever obtained - earlier this year in June, the gas mysteriously decreased back to background levels.

NASA believes that the source is a transient methane plume. “The methane mystery continues," said Ashwin Vasavada, a project scientist working on NASA’s Curiosity rover. "We're more motivated than ever to keep measuring and put our brains together to figure out how methane behaves in the Martian atmosphere." ®

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