Several years ago, NASA’s Curiosity rover detected traces of methane in the Martian atmosphere at levels significantly higher than the usual background. However, a few months later, the methane vanished, only to reappear later that year. This observation raised the intriguing possibility of life still lingering on Mars, as such fluctuations in methane could suggest biological activity.
While Mars was once home to liquid water oceans and a thick atmosphere, it is now a barren wasteland. So, what kind of life could possibly survive there? Most Earth organisms wouldn’t last long under Martian conditions, but there is a group of Earthly life forms that might find Mars more hospitable.
These are methanogens—single-celled organisms that consume hydrogen for energy and produce methane as a byproduct. Methanogens thrive in extreme environments on Earth, and a similar type of organism could be responsible for the seasonal fluctuations in methane levels on Mars.
In a recent paper submitted to Astrobiology, a team of scientists examined Earth’s environments to find potential analogs to Martian conditions, with a particular focus on methanogens thriving in environments similar to those that might exist on Mars.
The researchers identified three Earth environments where methanogens flourish under extreme conditions. The first is deep within the Earth’s crust, where small cracks in the rock allow liquid water to seep in, sometimes at depths of several kilometers.
The second is lakes buried beneath the Antarctic ice sheet, where the immense pressure from the ice keeps the water in a liquid state. The third is in super-saline, oxygen-deprived basins found at the ocean’s depths.
All three environments have analogs on Mars. Like Earth, Mars may have liquid water trapped deep within its crust. Its polar caps might also hide liquid water lakes beneath the ice. Moreover, there is controversial, yet intriguing, evidence of briny water flowing on Martian crater walls.
In their study, the researchers mapped the temperature ranges, salinity levels, and pH values of these Earth sites, measuring the abundance of molecular hydrogen and identifying where methanogens were most abundant. Next, they applied these findings to data gathered from Mars, pinpointing areas that might have the right conditions for life. They concluded that Acidalia Planitia, a vast plain in Mars’ northern hemisphere, is the most promising location.
Specifically, several kilometers below this plain, temperatures are warm enough to maintain liquid water. That water could possess the right combination of pH, salinity, and dissolved hydrogen to support methanogen-like organisms.
The next challenge is figuring out how to reach this potential hotspot for life.
