page_title: Methane on Mars
section_title: History of detections
hierarchical_section_title: Methane on Mars / History of detections
context_page_description: The reported presence of methane in the atmosphere of Mars is of interest to many geologists and astrobiologists, as methane may indicate the presence of microbial life on Mars, or a geochemical process such as volcanism or hydrothermal activity.
  Since 2004, trace amounts of methane have been reported in various missions and observational studies. The source of methane on Mars and the explanation for the enormous discrepancy in the observed methane concentrations are still unknown and are under study. Whenever methane is detected, it is rapidly removed from the atmosphere by an efficient, yet unknown process.
context_section_description: Methane (CH₄) is chemically unstable in the current oxidizing atmosphere of Mars. It would quickly break down due to ultraviolet (UV) radiation from the Sun and chemical reactions with other gases. 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. In March 2004, the Mars Express science team suggested the presence of methane in the atmosphere at a concentration of about 10 ppbv. This was confirmed soon after by three ground-based telescope teams, although large differences in the abundances were measured between observations taken in 2003 and 2006. This spatial and temporal variability of the gas suggests that the methane was locally concentrated and probably seasonal. It is estimated that Mars must produce 270 ton/year of methane.
  In 2011, NASA scientists reported a comprehensive search using ground-based high-resolution infrared spectroscopy for trace species (including methane) on Mars, deriving sensitive upper limits for methane (< 7 ppbv), ethane (< 0.2 ppbv), methanol (< 19 ppbv) and others (H₂CO, C₂H₂, C₂H₄, N₂O, NH₃, HCN, CH₃Cl, HCl, HO₂ – all limits at ppbv levels).
  In August 2012, the Curiosity rover landed on Mars. 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. However, the Trace Gas Orbiter (TGO) can measure these ratios and point to their origin.
  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, later calculated to a baseline of 0.3 to 0.7 ppbv.  In 2013, NASA scientists again reported no detection of methane beyond a baseline. 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. 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. Before and after that, readings averaged around one-tenth that level. On 7 June 2018, NASA announced the confirmation of a cyclical seasonal variation in the background level of atmospheric methane. The largest concentration of methane detected in situ by the Curiosity rover shows a spike to 21 ppbv, during an event in late June 2019. The Mars Express orbiter happened to be performing spot tracking in that area 20 hours before Curiosity's methane detection, as well as 24 and 48 hours after the detection, and the TGO was performing atmospheric observations at around the same time but at a higher latitude.
  The Indian Mars Orbiter Mission, which entered orbit around Mars on 24 September 2014, is equipped with a Fabry–Pérot interferometer to measure atmospheric methane, but after entering Mars orbit it was determined that it was not capable of detecting methane, so the instrument was repurposed as an albedo mapper. As of April 2019, the TGO showed that the concentration of methane is under detectable level (< 0.05 ppbv).
  The Perseverance rover and the Rosalind Franklin rover will not be equipped to analyze the atmospheric methane nor its isotopes, so the proposed Mars sample-return mission in the mid-2030s seems the earliest a sample could be analyzed to differentiate a geological vs biological origin.
caption: Model of a methane (CH4) molecule
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