The prospect of finding life on another planet is certainly a thrilling one. Over the years, scientists have tried to theorize how life started on our own planet in order to predict how life could begin in other habitable planets. In particular, researchers have been interested in microbes living in “extreme” environments since some of these are thought represent some of the oldest forms of life on Earth. These ancient and highly specialized organisms, called “extremophiles”, are thought to be able to grow pretty quickly in harsh conditions and are therefore an attractive candidate for the existence of life on other planets.
In line with this, researchers from the University of Arkansas have been investigating extremophilic organisms and exposing them to Mars-like conditions to see how they fare. In particular, they wanted to see if two species of methanogens could withstand Martian freeze-thaw cycles.
Methanogens are microorganisms within the domain archaea which is a domain distinct from bacteria. They’re actually responsible for the methane in the belches of ruminants and the flatulence of humans. Methanogens are methane producing anaerobic organisms, some of which use hydrogen to reduce carbon dioxide into methane. Because these organisms are anaerobic and non-photosynthetic, some scientists believe that they could be an ideal candidate for life on Mars; in particular, it is thought they could exist in sub-surface environments.
In order to test their survivability in Mars-like conditions, scientists exposed M. formicicum and M. wolfeii to Martian freeze-thaw cycles that are far below the ideal growth temperature of these organisms (37oC and 55oC, respectively). These organisms are in fact both thermophiles, which are extremophilic organisms that thrive at relatively high temperatures. The scientists found that both species survived the Mars-like temperature ranges in the laboratory.
“The low temperature on Mars inhibited their growth, but they survived,” said Rebecca Mickol, one of the researchers involved in the study, in a news-release. “Once they got back to a warm temperature, they were able to grow and metabolize again. I wanted to see if these cold temperatures would kill them, or if they were able to survive and adapt.”
According to Mickol, the temperature of Mars can range from between -90oC and 27oC in just one Martian day. “If any life were to exist on Mars right now, it would at least have to survive that temperature range. The survival of these two methanogen species exposed to long-term freeze/thaw cycles suggests methanogens could potentially inhabit the subsurface of Mars,” she added.
Back in 2004, methane was discovered in the atmosphere of Mars. Lead researcher of this study Timothy Kral believes it is possible that methanogens are the source of this methane, and has been studying the ability of these organisms to withstand Mars-like conditions since the ‘90s.
Of course, just because these organisms can survive these dramatic temperature ranges, this does not necessarily mean that methanogens can survive on Mars. It’s a little more complicated than that. It isn’t clear whether the researchers also replicated other conditions found on Mars besides these temperatures. But it's a very interesting study that certainly demonstrates the capability of these organisms to survive some of the harsh conditions found on Mars.