Among the recent discoveries about Mars is the large amount of methane in the Martian atmosphere. Methane cannot last long on Mars, and so must be constantly replaced. Most of the methane on Earth is produced by living organisms. Could this mean that there is also life on Mars?
There are several other possibilities for what could be replenishing the Martian methane. One is that the methane is caused by volcanic activity. Unfortunately for this hypothesis, Mars does not seem to have any active volcanoes.
Another possibility is that the methane is renewed by meteorites. As meteorites enter the planet’s atmosphere, they vaporize in a reaction that releases methane. This seemed like the most promising answer until a study was conducted by Richard Court of Imperial College, London.
Using a technique called quantitative pyrolysis Fourier transform infrared spectroscopy, he simulated the effect of falling meteorites in his lab. Combined with the numbers of meteorites falling on Mars, he calculated that meteorites could only account for some 10 kg out of the 100 to 300 metric tons required to maintain the level of methane in the atmosphere.
Two remaining theories are that the methane is released from clathrates (methane trapped within water ice crystals), and of course, that the methane is produced by microorganisms in or below the Martian soil.
One way to determine whether the latter explanation is the correct one is to measure isotope ratios in methane and in water on Mars. Because living organisms preferentially use lighter isotopes, organically produced methane will have a different isotopic ratio than water.
View of Mars from Hubble Space Telescope, created by Nasa and ESA, June 26, 2001.