Methane has been detected on Mars, which is a possible indicator of past or present life on the Red Planet.
The gas was detected by NASA’s Curiosity rover, which has been taking samples that have revealed a constant low-level of methane, as well as various spikes of up to 10 times normal levels. The spikes are incredibly interesting to scientists, because on Earth 95% of methane is produced by microbial organisms.
Methane on Mars: Where does it come from?
Curiosity has so far been unable to identify the source of the gas on Mars, but it is hoped that it might indicate the presence of life. However up to this point scientists believe it is most likely that there are underground stores of methane that are sometimes disturbed, leading to the spikes.
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Methane could be released from so-called clathrates, which Curiosity scientist Sushil Atreya defined as “molecular cages of water-ice in which methane gas is trapped.” The presence of methane still leaves us without an explanation as to how it got there, whether it be from Martian insects, or from a natural process known as serpentinisation, which produces methane when water interacts with specific types of rock.
In over two years since it landed, Curiosity had previously struggled to detect methane which had been spotted by orbiting spacecraft, and even by Earth-based telescopes. The veracity of these sightings was thrown into doubt, but Curiosity has since proved that they were correct.
The robot has been analyzing Martian air since it landed in August 2012, and has discovered a consistent signature of around 0.7 parts per billion by volume of methane, compared to 1,750 parts per billion on Earth. Curiosity has observed four spikes in methane levels over a 2-month period, with levels ranging from 7 to 9 parts per billion by volume.
Curiosity is currently located in a deep bowl known as Gale Crater, and researchers claim that it is likely that the gas is being released from within the crater or close to its edge. Readings suggest that the gas is being released from north of the robot’s current location.
It would be possible to determine the origins of the methane by analyzing the isotopes of carbon in the gas, but this kind of testing is made impossible by the small samples collected so far. Scientists are waiting for another peak in order to enrich a sample which might be large enough to enable them to carry out the appropriate analysis.