Issues Magazine

Life on Mars? Curiosity Rover Detects No Methane

Source: 

NASA

Data from NASA's Curiosity rover has revealed that the Martian environment lacks methane. This is a surprise to researchers because previous data has indicated positive detections.

Whether the Martian atmosphere contains traces of the gas has been a question of high interest for years because methane could be a potential sign of life.

“This important result will help direct our efforts to examine the possibility of life on Mars,” said Michael Meyer, NASA's lead scientist for Mars exploration. “It reduces the probability of current methane-producing Martian microbes, but this addresses only one type of microbial metabolism. As we know, there are many types of terrestrial microbes that don't generate methane.”

Curiosity analysed samples of the Martian atmosphere for methane six times from October 2012 through to June 2013 and detected none. Given the sensitivity of the instrument used, scientists calculate the amount of methane in the Martian atmosphere today must be no more than 1.3 parts per billion – about one-sixth as much as some earlier estimates.

“It would have been exciting to find methane, but we have high confidence in our measurements, and the progress in expanding knowledge is what's really important,” said Chris Webster of NASA's Jet Propulsion Laboratory. “We measured repeatedly from Martian spring to late summer, but with no detection of methane.”

Previous reports of localised methane concentrations up to 45 parts per billion on Mars, which sparked interest in the possibility of a biological source on Mars, were based on observations from Earth and from orbit around Mars. However, the measurements from Curiosity are not consistent with such concentrations, even if the methane had dispersed globally.

“There's no known way for methane to disappear quickly from the atmosphere,” said Sushil Atreya of the University of Michigan, Ann Arbor. “Methane is persistent. It would last for hundreds of years in the Martian atmosphere. Without a way to take it out of the atmosphere quicker, our measurements indicate there cannot be much methane being put into the atmosphere by any mechanism.”

The highest concentration of methane that could be present without being detected by Curiosity's measurements so far would amount to no more than 10 –20 tons per year of methane entering the Martian atmosphere, Atreya estimated. That is about 50 million times less than the rate of methane entering Earth's atmosphere.