Natural methane on Mars

Therefore, a persistent or episodic presence of methane in the atmosphere may imply the existence of a source to continually replenish the gas.

The first evidence of methane in the atmosphere was measured by ESA's Mars Express orbiter with an instrument called the Planetary Fourier Spectrometer.

The rover's instruments are capable of making precise abundance measurements, but cannot be used to distinguish between different isotopologues of methane and so it cannot determine if it is geophysical or biological in origin.

[15] The first measurements with Curiosity's Tunable Laser Spectrometer (TLS) in 2012 indicated that there was no methane —or less than 5 ppb— at the landing site,[25][26][27] later calculated to a baseline of 0.3 to 0.7 ppbv.

[29][30][31] But in 2014, NASA reported that the Curiosity rover detected a tenfold increase ('spike') in methane in the atmosphere around it in late 2013 and early 2014.

[10] Four measurements taken over two months in this period averaged 7.2 ppbv, implying that Mars is episodically producing or releasing methane from an unknown source.

[32][33][10] On 7 June 2018, NASA announced the confirmation of a cyclical seasonal variation in the background level of atmospheric methane.

[34][35][36] The largest concentration of methane detected in situ by the Curiosity rover showed a spike to 21 ppbv, during an event in late June 2019.

[45] It has also been shown that methane could be produced by a process involving water, carbon dioxide, and the mineral olivine, which is known to be common on Mars.

An analog on Earth suggests that low-temperature production and exhalation of methane from serpentinized rocks may be possible on Mars.

[50] Under the assumption of a cold early Mars environment, a cryosphere could trap such methane as clathrates in a stable form at depth, which might exhibit sporadic release.

[66] A team from the Italian National Institute for Astrophysics suspects that the methane detected by the Curiosity rover may have been released from a nearby area called Medusae Fossae Formation located about 500 km east of Gale crater.

[78] Another hypothesis is that methane reacts with tumbling surface sand quartz (silicon dioxide SiO2) and olivine to form covalent Si – CH3 bonds.