There are potential geological processes that could produce methane too, but even before identifying the source of the gas on Mars, scientists have been trying to solve another mystery.
The detections of methane aren’t consistent. Some instruments, such as NASA's Curiosity Rover, have repeatedly detected the gas above the surface of the Gale Crater. Others, such as ESA's(European Space Agency) ExoMars Trace Gas Orbiter, haven’t found any traces of methane higher up in the Martian atmosphere.
“When the Trace Gas Orbiter came on board in 2016, I was fully expecting the Orbiter team to report that there’s a small amount of methane everywhere on Mars”, said Chris Webster, lead of the Tunable Laser Spectrometer(TLS) instrument in the Sample analysis of Mars(SAM) chemistry lab aboard the Curiosity Rover
The TLS has measured less than one-half part per billion in volume of methane on average in Gale Crater. That’s equivalent to about a pinch of salt diluted in an Olympic size swimming pool. These measurements have been punctuated by baffling spikes of up to 20 parts per billion in volume.
The study published in the Astronomy and Astrophysics Journal states that the quantity, distribution, and behavior of methane in the Martian atmosphere are of great interest since the gas is recognized as a potential biosignature for microbes to flourish.
Some scientists had even suggested that the Rover might itself be releasing the gas as it moved ahead crushing rocks and due to the degradation of its wheels. However, a deep analysis of the machine showed no such chemical reaction happening on Curiosity Rover.
While the study suggests that methane concentrations rise and fall throughout the day at the surface of Gale Crater, scientists have yet to solve the global methane puzzle at Mars. Methane is a stable molecule that is expected to last on Mars for about 300 years ago before getting torn apart by solar radiation. If methane is constantly seeping from all similar craters, which scientists suspect is likely that Gale doesn’t seem to be geologically unique, enough of it should have accumulated in the atmosphere for the Trace Gas Orbiter to detect. Scientists suspect that something is destroying methane in less than 300 years.