An Unexpected Methane Surge Detected on Mars

Among the numerous findings on Mars, the presence of methane in its atmosphere is arguably the most fascinating. This discovery holds potential historic significance, as methane on Earth is often linked to biological activity. On Mars, this could imply – *cue dramatic pause* – extraterrestrial life!

Alternatively, it might signify absolutely nothing.

The Mars methane mystery made waves once more as NASA revealed findings from the Mars rover Curiosity, equipped with advanced tools to analyze the Martian atmosphere. The rover, weighing one ton, is currently exploring Mount Sharp, a towering 3-mile (nearly 5-kilometer) mountain within Gale Crater, where layers of Mars' geological history are exposed for the rover's sophisticated instruments to examine.

This latest discovery isn't tied to rocks or dust but lies in the air. Curiosity identified a record-breaking methane "spike" using its Sample Analysis at Mars (SAM) tunable laser spectrometer. The rover detected a short-lived methane burst with a concentration of 21 parts per billion units per volume (ppbv). While this amount may seem negligible, on Mars, it's a significant finding.

"The methane puzzle persists," stated Ashwin Vasavada, Curiosity's project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, in a statement. "We're more determined than ever to continue our measurements and collaborate to understand methane's behavior in the Martian atmosphere."

This recent detection is even more puzzling because, when scientists conducted a follow-up analysis shortly after the record-breaking find, methane levels had dropped back to just one ppbv, the baseline concentration Curiosity regularly detects.

So, What's Going on With Mars Methane?

On Earth, home to a diverse and intricate ecosystem of countless life forms, methane concentrations are thoroughly understood and, due to human activities, are on the rise – recently reaching a global peak of 1,866 ppbv, the highest in 800,000 years. (This is alarming for our planet's future, as methane is a powerful greenhouse gas.) While the 21 ppbv detected on Mars may seem insignificant in comparison, even a brief accumulation could hint at the presence of life.

Before scientists can claim Mars methane as evidence of "tiny Martians," they must determine whether it originates from methane-producing microbes beneath the surface or a less thrilling source. Unfortunately, while Curiosity can identify extremely low methane levels, it cannot pinpoint the source. (And no, flatulent Martian cows are not a plausible explanation.)

"With our current capabilities, we cannot determine if the methane comes from biological or geological processes, or whether it's ancient or recent," stated Paul Mahaffy in a statement. Mahaffy is the principal investigator for SAM at NASA's Goddard Spaceflight Center in Greenbelt, Maryland.

Microbes or Geology?

Methanogens, a well-researched group of single-celled microorganisms on Earth, flourish in oxygen-free environments (oxygen can even be harmful to many of them). They inhabit damp areas, such as marshes, and reside in the digestive systems of animals (including cows and humans), producing methane as they break down carbon dioxide and hydrogen for energy. However, methane can also be generated through non-biological, geochemical processes. For instance, when water interacts with certain minerals, a reaction called serpentinization can occur, releasing methane as a byproduct.

While most of Earth's methane is produced through biological processes, the situation on Mars remains unclear. It's possible that underground water is reacting with rocks beneath Curiosity, releasing methane that seeps to the surface. Alternatively, there could be vast colonies of methanogen-like microbes on Mars, producing methane in bursts that explain the sudden spikes detected by Curiosity.

One thing is clear: Methane is highly unstable when exposed to ultraviolet light. Without an ongoing source, methane would not exist in Mars' atmosphere, as the sun would have destroyed it. Scientists are certain that something is actively generating the gas, whether through geological or biological means.

Lots of Questions About Mars Methane, Few Answers

While every Mars methane discovery sparks thrilling "life on Mars" headlines, the story isn't new. The gas was first identified by the European Space Agency's Mars Express orbiter in 2004. This finding was confirmed in 2011 through Earth-based infrared observations that detected trace amounts of methane. The intrigue deepened a few years after Curiosity landed on Mars. Although the rover had only found minimal methane levels since its 2012 arrival, it recorded a notable methane spike in 2014. By 2018, NASA revealed that methane levels fluctuated seasonally. Scientists remain puzzled by these sporadic spikes, though the possibility of contamination in Curiosity's instruments hasn't been entirely ruled out.

The bottom line is that more research is needed to pinpoint the source of Mars' methane – and whether it's produced by microbial activity. With the European Trace Gas Orbiter (TGO), which reached Mars in late 2016, scientists aim to combine orbital and ground-based data to better understand methane emissions. However, as of now, the TGO has not detectedany methane – a puzzling absence that adds more mystery to Mars' enigmatic methane narrative.