Over the course of the seven Earth years that Curiosity has been exploring Mars, it has detected methane many times. In fact, previous reports have shown that the levels of methane actually seem to rise and fall seasonally.
Scientists have even noticed sudden spikes of methane. Unfortunately, the team knows very little about how long these transient plumes tend to last, or why they’re different than the seasonal patterns.
Last month I told you all about how Curiosity was planning to slowly venture up Mount Sharp to investigate several sights where water may once have existed. One of its first stops was at a clay-bearing unit. While investigating this area earlier in the week, Curiosity found something rather…curious: the largest amount of methane ever detected during this mission.
The total measurement is about 21 parts per billion by volume (ppbv). This finding is exciting because here on Earth this gas is produced by anaerobic bacteria as it decomposes plant matter under water.
However, methane is also found naturally near volcanic vents.
While the interior of the Red Planet is partially molten, scientists are not certain how much of the subsurface is liquid. In fact, there has been no measured volcanic activity on our rusty neighbor and the youngest volcano is believed to have erupted more than 500 million years ago.
This makes the chances of methane occurring from volcanic activity far less likely to be the culprit.
Another way methane can be formed is from a reaction of carbon from carbonate rocks. Here’s how this works: methane is composed of 4 hydrogen atoms and 1 carbon atom. At the right temperatures, carbonate rocks (which naturally contain carbon dioxide) can interact with liquid water, thus forming methane.
Because Curiosity is exploring the clay-bearing unit where it is highly likely water once existed, the chances of this massive methane spike being from a geological reaction is the most probable.
Sadly, Curiosity doesn’t have the right instruments needed to definitively determine the source of the methane, or pinpoint whether it’s coming from a local source within Gale Crater or somewhere else on the planet, altogether.
“With our current measurements, we have no way of telling if the methane source is biology or geology, or even ancient or modern,” said Paul Mahaffy, SAM Principal Investigator of NASA’s Goddard Spaceflight Center.
In the meantime, Curiosity’s scientists plan to analyze the findings and conduct more methane observations. Working with the European Space Agency’s Trace Gas Orbiter team to combine observations from surface to orbit, scientists may be able to finally locate sources of the gas and understand how long it lasts in the Martian atmosphere.
And even if the findings prove to be of geologic reactions, this still bodes well for proving water may still exist beneath the surface of Mars.