You might remember when we accused Curiosity of tooting a cheeky martian fart up on Mars. It was thought that Curiosity's own reserve of methane gas, used to analyze samples, might be a source of contamination since there were some distinct methane spikes.
However, new evidence published in Nature Communications might just put Curiosity in the clear from being accused of detecting its own methane. The results suggest that there might be methane on Mars after all.
Six martian meteorites that fell to Earth were analyzed using a method called the crush-fast scan technique. This involves crushing samples of meteorite to release the gases trapped within. After analyzing each individual burst of gas, the researchers found they were dominated by methane, carbon dioxide, hydrogen and nitrogen.
Meteorite crusts undergo a bit of thermal alteration when they enter the Earth's atmosphere. Fortunately, the scientists considered this before starting research and avoided sampling any of the fusion crust (the burnt bits). Some of these meteorites fell to Earth as long ago as 1911 (this is when the Nakhla meteorite tumbled to Egypt), so there is also the possibility that they are contaminated with Earthen air. The level of gaseous oxygen in the meteorite is a good starting indicator for how much they are contaminated since Martian atmosphere has next to no oxygen. One meteorite (Y000749) contained next to no oxygen and was a good representative of the Martian atmosphere. However, the other meteorites had more oxygen than this, which indicates they are contaminated with air from Earth.
The discovery of methane on the Red Planet has had a major influence on Mars exploration. The presence of methane implies there might be life on the planet producing it, most likely in the form of a microorganism.
However, there are mechanisms that can take place that produce methane without the influence of life—for example, serpentinization. This has nothing to do with serpents. Instead, it is a geological process where rocks are changed when water is introduced to the minerals in the stone. Scientists have located olivine on Mars, a mineral that undergoes the serpentinization process. The changing rocks release hydrogen gas and certain alloys in the rock can act as a catalyst for the formation of methane and other hydrocarbons.
Another more exciting possibility would be from biological sources producing methane. The main candidate at the moment is microorganisms, called methanogens, which produce methane as part of their metabolic function.
The composition of the meteorites are such that water could be responsible for the production of methane before they were ejected from Mars. There is also research that suggests this methane could survive the journey to Earth.
This could be great news for new missions that are eager to join the rovers currently scouting the surface of the Red Planet. The Exomars Orbiter is popping over to Mars in 2016 in search of more methane signals. It looks like there might be reason to be optimistic since these crushed meteorites suggest methane is present on the planet's crust.