NASA’s Curiosity rover on Mars has confirmed the existence of methane, which is a molecule that can potentially be produced by microbial life.
Methane cannot survive for long in the Martian atmosphere and models predict that it should only exist for 300 years after being produced. This makes the detection of methane on Mars an exciting prospect as it must have been recently produced by geological or biological activity.
In 2003, plumes of methane were supposedly detected by ground-based telescopes on Earth. However this was met with doubt from some scientists as the methane spectral lines coincided with methane lines in the Earth’s atmosphere.
Methane is also thought to have been detected from Mars orbit by the Mars Global Surveyor and Mars Express, but these measurements are far from concrete evidence.
“In general the Mars orbit measurements are of low signal to noise, which is only achieved after averaging tens of thousands of collected spectra,” Christopher Webster, lead author of the Science paper on the Martian methane, told the author. “These spectra are ‘patchy’ and show spatial distributions and maxima very different from the ground-based plumes.”
This made Curiosity’s definite detection of methane very welcome in the astronomical community. Curiosity used the Sample Analysis of Mars (SAM) instrument to directly measure the level of methane over the last 20 months.
The results show that the background levels are much lower than previously thought, as well as revealing significant peaks in the methane levels over a period of 60 Martian days. The elevated methane levels then dropped rapidly, which implies that it was produced by a local source that then dispersed quickly.
While microbes can produce methane, there are also a number of non-biological processes that can create it. For instance, methane can be released as ultraviolet light degrades interplanetary dust particles and meteorites that have fallen on to Mars. Erosion of basalt containing methane or heating of methane ice are other possible abiotic sources.
“When we detect a signal – like this methane – we have to understand where it comes from, and by doing that we’ll learn new things about how planets work,” explained Lisa Kaltenegger, a professor at Cornell University. “Figuring out if this methane on Mars, at our doorsteps, is geological or could be a signal for life is an exciting stepping stone towards finding life outside our solar system as well.”
Identifying the source of the methane will be no easy task and will most likely have to wait for a future mission to Mars.
Meanwhile, Curiosity rover has taken another “selfie” showing itself at a site called Mojave, at the foot of Mount Sharp. It combines dozens of separate images made by the Mars Hand Lens Imager (MAHLI) camera at the end of its robotic arm in January, 2015.