During a follow-up test over the weekend, though, scientists found that the methane levels around the rover already dropped sharply. Curiosity detected normal methane levels (1 part per billion by volume) following the sudden elevation, suggesting that the abnormally high values came from transient methane plumes. So, what does that mean? Well, Paul Mahaffy, the principal investigator for Curiosity’s Sample Analysis at Mars instrument, said during a townhall event: “A plume came and a plume went.”

Curiosity unfortunately doesn’t have the instruments to determine whether the source of methane is biological or geological. Further, scientists have yet to figure out a pattern for Martian’s transient plumes. In other words, they’re still nowhere close to unraveling the planet’s methane mystery. They need to gather more information through Curiosity and from other missions to gain a deeper understanding of the plumes. When they finally understand where the plumes are coming from, maybe then they can figure out whether the presence of methane on the red planet truly is a sign of life.

Ashwin Vasavada, Curiosity project scientist at NASA’s JPL, said:

“The methane mystery continues. We’re more motivated than ever to keep measuring and put our brains together to figure out how methane behaves in the Martian atmosphere.”

Just what would produce the methane isn’t clear. It could represent recent or even current microbial life (possibly underground), but it could also geothermal reactions or ages-old methane finally escaping to the surface. The one certainty is that any gas will have appeared relatively recently — reactions with sunlight and chemicals would split the molecules within centuries.

If scientists can confirm the presence of methane, the greater challenge is finding ways to study it in more detail. The Mars 2020 rover and other upcoming vehicles are meant to look for the ingredients of life, but not to verify the possibility of existing life. It could be a long time before there’s a definitive pronouncement on what the gas represents.

Their idea is to use microbes to convert excess renewable energy into methane, which could be burned as needed. In nature, the microorganism Methanococcus maripaludis consumes hydrogen and carbon dioxide and exudes methane. So, the researchers are using renewable energy-powered electrodes to split water and free its hydrogen atoms. Those hydrogen atoms are fed to the microbes, which then pull carbon dioxide from the air and release methane. The gas doesn’t dissolve in water, so it can be captured and stored.

Then, at times of peak demand or when renewables aren’t producing, the methane can be burned much like fossil fuel sources. It might seem backwards to turn renewable energy into methane, which releases carbon dioxide when it burns. But, this methane is produced by pulling carbon dioxide from the atmosphere, so the process is carbon-neutral. One significant advantage over battery storage systems, like Tesla’s Powerpacks, is that the methane can be converted into electricity using existing infrastructure.

The researchers are still working on the technology, but they believe this can be cost effective at scale. The Department of Energy has already committed funding, and the Lawrence Livermore National Laboratory and Southern California Gas are helping to develop more efficient designs. It’s hard to say if this can solve renewable energy’s biggest flaw — its storage problem — but it’s certainly a novel approach.

Researchers at @StanfordEng are hoping to turn a microorganism called Methanococcus maripaludis into a renewable energy storage system. https://t.co/5zVnYKtNaE

— Stanford University (@Stanford) April 3, 2019