NASA’s Mars Curiosity rover recently detected a high amount of methane in the planet’s surface air, a gas that’s often found as a byproduct of microbes. The team behind the mission is now running follow-up experiments over the weekend, the results of which are expected by Monday, according to an internal email obtained by The New York Times. Scientists working on other Mars missions, to include the Mars Express and ExoMars Trace Gas Orbiters, are also working with Curiosity’s team to verify the data and determine what the broader implications could mean.

The discovery of significant amounts of methane on the Martian surface may indicate recent life on the planet due to the way the gas interacts with sunlight and other chemicals, as also noted in the Times’ report. Any methane produced would only survive a few centuries, so amounts measurable today point to more recent emissions, or more specifically, ‘recent’ in terms of the huge time frames involved in planetary evolution.

Spikes in methane gas have been detected on Mars before, but the current readings demonstrate some of the highest levels indicated. Specifically, 21 methane parts per billion (ppb) were detected this week by Curiosity verses the 7 ppb detected in a 2013 spike and 1 ppb detected when the rover initially arrived on the red planet. The highest reading thus far was found in 2009 at 45 ppb using the NASA Infrared Telescope Facility and the telescopes at the W.M. Keck Observatory in Hawaii.

Seasonal cycle of methane on Mars as detected by NASA’s Curiosity rover in the Gale Crater. | Image: NASA/JPL-Caltech

The presence of methane on Mars has been a bit of a mystery as readings dedicated to the gas have varied in major ways. While telescopes and rovers have indicated its presence on the planet numerous times, results from the European Space Agency’s ExoMars Trace Gas Orbiter in December last year showed no sign of methane even down to 50 parts per trillion. This in itself could also be a positive indicator, though, albeit initially confusing. Variations in surface-level readings that stand in contrast to orbit-based atmospheric readings could be evidence that the methane is coming from the ground rather than space-faring visitors like comets.

Other theories that would explain the presence of methane without current biological life include geological processes. Cold Martian temperatures could mean that methane produced much earlier in the planet’s timeline was simply trapped in ice and is being released periodically by geological activity. Data analysis by Curiosity’s team earlier this year found a seasonal cycle of methane release near Mars’s Gale Crater which is full of ice and thought to be a dried lake bed.

Regardless of the source, the detection of methane on Mars indicates some sort of geological or biological activity. Earth itself is full of life in the most interesting places, to include inside very deep layers of ocean sediment, and we can likely look forward to exciting discoveries from our red neighbor no matter what’s ultimately determined about its methane source.