Curiosity obtained its most powerful detection of methane on Mars last week. In the Gale Crater, a region the rover has been exploring since it landed in 2012. Its laser spectrometer instrument recorded a methane spike of 21 parts per billion volume (ppbv).
Methane presence on Mars generally has a global average of 10 ppbv, so NASA is conducting follow-up studies to find out where the unexpectedly large concentration came from.
Our understanding of methane sources is what makes this so interesting. It can be emitted by living organisms. Tracking the origin of methane on Mars might, therefore, be a way to find out if there are microbes residing in the Red Planet’s extreme conditions.
But to get excited is way too early, as microbes are definitely not the only potential source.
“With our current readings, we have no way to tell whether the origin of methane is biology or geology, or even ancient or modern,” said NASA’s Goddard Spaceflight Center Mars researcher Paul Mahaffy.
Over the years, curiosity and other instruments have found a few methane detections, but levels seem to increase and decrease, and as a mischievous ghost, methane appears and disappears.
It wasn’t until earlier this year that two independent instruments were realized by researchers that the same methane puff was identified in 2013. It is quite difficult to track down where it comes from and what’s creating it.
And there are reasons to jump to any significant findings with caution. We have a fair amount of methane here on Earth-about 1,800 ppbv in the atmosphere as of 2011. 90 to 95 percent of which is generated by living or deceased creatures.
But if we look elsewhere in the Solar System, there are also plenty of geological procedures that can abiotically produce methane without the presence of life. Quite enough methane has appeared through chemical reactions on gas and ice giants such as Jupiter, Saturn, Uranus, and Neptune.
Pluto has ice of methane. Saturn’s moon Titan has liquid methane lakes. In the Solar System, the compound is not precisely rare, but as far as we understand, only Earth’s is a product of biological methods.
In the works, there is another spanner. The ExoMars Trace Gas Orbiter of the European Space Agency has been gathering data for a little over a year, with the capacity to detect 50 parts of methane per trillion by volume in the Martian atmosphere and has so far emerged totally empty handed.
So before dissipating into the atmosphere, whatever methane is on Mars could only exist very briefly on the surface.
Current observations will assist to find out more about this detection. Whatever they discover-whether Curiosity detects the methane again or not-NASA researchers will have more context to determine whether the gas was transient or local to the Gale Crater.
They were also in touch with the ESA’s Trace Gas Orbiter team to see if there was consequent atmospheric detection. This could assist in locating the gas source and calculating how long it will last in the atmosphere.
Whether the origin of methane is biological or not, it will teach us something fresh about Mars to figure out where it comes from.