Is Mars undergoing Global Warming? Data from Curiosity suggests it might be
Using its Sample Analysis at Mars (SAM) tunable laser spectrometer, NASA’s Curiosity rover has detected the highest concentration of methane ever found in the Martian atmosphere, in the Teal Ridge region of Gale Crater.
Methane has been found on many occasions in Mars’ atmosphere and in surface samples. Levels of atmospheric methane have been seen to rise and fall as the planet’s seasons change. On several occasions, Curiosity measured spikes in methane levels in the form of transient plumes. The cause of these spikes remains unknown, as does their difference from the more predictable seasonal methane level changes.
On Wednesday, June 19, Curiosity measured methane levels three times that recorded during a similar spike that occurred in 2013 over several months. Gases are measured in terms of parts per billion units of volume (ppbv). If a gas measures one part per billion units of volume, that means one billionth of a volume of air consists of that particular gas. In the 2013 spike, Curiosity detected seven parts per billion units of volume of atmospheric methane. This time, it recorded 21 parts per billion units of volume, a level that scientists described as “startlingly high.”
Finding such levels of methane is a significant discovery in terms regarding the search for microbial life on Mars because one way the gas is produced is through biological processes. However, it can also be produced by geological processes, specifically through interactions between rock and water.
On Earth, methane is considered to be one of the key gasses responsible for Global Warming and rising levels can be traced back to human activity, farm animals and other sources.
In theory, methanogens, or microbes that live underground and do not need oxygen to survive, could be generating methane beneath the Martian surface as a byproduct of their metabolic processes. Unfortunately, Curiosity has no way to detect whether the methane it measured is coming from biological or geological sources. The rover cannot even be certain whether the gas is being generated locally on Gale Crater or is coming from another part of the planet. Naturally, the levels of methane on Earth, as well as their sources, are not the same as those on Mars.
“With our current measurements, we have no way of telling if the methane source is biology or geology, or even ancient or modern,” explained SAM principal investigator Paul Mahaffy of NASA’s Goddard Space Flight Center in Maryland. Because methane is broken down within several hundred years by sunlight and chemical reactions, its current discovery indicates it cannot be extremely old.
One possibility is that the methane is coming from deep within the planet. Another is that it is being generated by geothermal reactions connected to water and heat, a theory suggested by scientists back in 2004, when methane was discovered on Mars’ surface.
The discovery is significant enough that the rover has been diverted from its planned research activity to follow up and determine whether or not the methane came from a transient plume. Mission scientists plan to consult with other science teams, including those of the European Space Agency‘s (ESA) Mars Express orbiter and Trace Gas Orbiter (TGO), especially since to date, the TGO has not detected any methane in the Martian atmosphere. Working together, the science teams hope to find the source of the methane and determine how long it stays in the atmosphere before dissipating.
Curiosity‘s scientists have already pioneered a new technique that will enable the rover to detect extremely low levels of methane.
Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.