Last week, NASA's Mars Curiosity rover has detected high amounts of potentially life-indicating methane from its location inside Gale Crater.
The six-wheeled robot reported methane levels around 21 parts per billion units by volume (ppbv). It is far higher than the usual background concentration in the area, which ranges from about 0.24 ppbv to 0.65 ppbv.
Is There Life On Mars?
The large presence of methane is exciting because, on Earth, the gas is produced by microbes and other organisms. However, methane can also be generated abiotically through geological processes, like the interaction between water and rocks.
To investigate, Curiosity spent the past weekend performing follow-up experiments. If the unusually high levels of methane are confirmed by the rover, the next step is to locate the source of gas and determine what is producing it.
On Monday, June 24, NASA released an update. The space agency revealed that the methane detected last week was a transient plume. A similar phenomenon has been observed in the past, but it was the largest amount of methane that the rover has found on Mars since its arrival in 2012.
This past weekend, the level of methane went down to 1 part per billion by volume on early Monday morning. This was closer to the background levels in Gale Crater that Curiosity observes all the time.
Unfortunately, there is no way to say whether the plume of methane was caused by normal geological processes on Mars or if Curiosity has stumbled upon signs of microbial life on the Red Planet. The rover does not have the right instruments to make that kind of assessment.
Mystery Of The Martian Methane Plume
Scientists have detected methane on Mars as far back as the 70s with the Viking missions. More recently, Curiosity sniffed out spikes in methane levels (peaking at around 6 or 7 ppbv) in June 2013 and from late 2013 to early 2014.
NASA, however, has not seen a pattern of the occurrence of these transient plumes.
"The methane mystery continues," said Ashwin Vasavada, Curiosity project scientist at the Jet Propulsion Laboratory. "We're more motivated than ever to keep measuring and put our brains together to figure out how methane behaves in the Martian atmosphere."
The U.S. space agency is set to launch the Mars 2020 rover designed specifically to look for evidence of past habitable conditions and past microbial life on the Red Planet.
