A Recent Discovery Could Unravel the Mystery of Martian Methane
A Window to Life in the Deep Subsurface
A science team headed by researchers from McGill University in Montreal, Canada, reported their latest finding from the Lost Hammer Spring, located in the High Arctic of Nunavut in Canada. The discovery of the spring and its inhabiting microbial community is exciting because it is a close analog to a possible life-containing habitat at or very close to the Martian surface.
The research team’s goal was to identify the microbial composition of the Lost Hammer Spring, which they achieved with a variety of state-of-the-art DNA-based analyses. They found that the site represented a rare habitat on Earth’s surface. The Lost Hammer Spring is literally a window into the Martian deep subsurface. The spring discharges oxygen-poor water at sub-freezing temperatures (-50C), but the water is kept liquid by its high degree of salinity (24%). For the water to reach the surface, it travels upwards through 600 meters of Arctic permafrost.
The active microbial community inhabiting the Lost Hammer Spring is dominated by sulfur-oxidizing bacteria and methane-oxidizing archaea. The methane-oxidizing archaea are not surprising because the spring also releases a lot of gas, primarily composed of methane (about 50%). Their results demonstrate Mars-relevant microbial lifestyles, including the cycling of sulfur, the oxidation of methane and trace gases (hydrogen and carbon dioxide) under oxygen-poor, hypersaline, and sub-zero environmental conditions. Thus, the McGill research team’s findings show that microbial life could survive in similar extreme habitats on Mars.
Methane was detected on Mars by Earth-based telescopes and an orbiting spacecraft and later was confirmed by the Curiosity Rover. It is one of the remaining and hotly discussed mysteries related to possible life on Mars. Explanations range from chemical reactions to the presence of methane hydrates, which might have been formed by early life on Mars. An especially intriguing hypothesis is that the methane is produced by currently active life on the Red Planet.
The JPL-led science team that reported the methane detected by the Curiosity Rover pointed out that the rover observed sudden peak releases of methane at Gale Crater and that these releases appeared to derive from unidentified local sources. Could the sources be springs at or near Gale Crater, like the Lost Hammer Spring on Earth, releasing methane into the cold Martian air? Renewed efforts should be undertaken to identify the locations of the methane releases on Mars. If a spring would really be the source, it presents a prime location for a later life-detection experiment.
Even if methane-releasing springs don’t exist on Mars, the identified microorganisms by the McGill research team inform us about the extremophilic limits of life, both in regard to low temperatures and high salinity levels. This is important to know for Mars and potentially habitable planetary environments like the ones below the ice covers of Europa and Enceladus because, in all these locations, high concentrations of salts are thought to keep the briny water liquid at sub-zero temperatures.