Astrobiologists have been worried for quite some time now that the Martian surface has been contaminated with microbes originating from Earth — what got there by clinging to all the various probes and artifacts we've sent there. But given how severe the conditions are on Mars, it has been generally assumed that this is likely an impossibility.
A recent study now threatens to overturn this sentiment. Researchers from Russia and the U.S. have demonstrated that a hardy bacterium found in Siberia is in fact capable of surviving Mars-like conditions — a revelation that will have profound implications on how we prepare our Mars-bound artifacts for future missions.
To conduct the study, researchers from the University of Florida and the Russian Academy of sciences extracted various strains of bacteria found in the Siberian permafrost off the banks of the Kolyma River — extremophiles that can survive some of the harshest conditions that Earth has to offer. The samples were taken from a depth of 12 to 20 meters (40 to 65 feet) where the soil has an average temperature of -7 °C (19 °F).
The samples were drilled out directly from the depth of the permafrost, and without fluid (which normally serves as lubrication) to avoid any contamination. The microbes that were taken had endured their conditions deep underground for the past 6,000 to 8,000 years.
The team, which consisted of Wayne Nicholson, Kirill Krivushin, David Gilichinsky and Andrew Schuerger, then grew larger cultures of these microbes back at the lab at normal temperatures in preparation for the next phase.
The researchers took these cultures and exposed them to similar conditions found on Mars, including a severe lack of oxygen, extreme cold temperatures, and very low pressure (about 150 times lower than the Earth's, about 7 millibars). The experiment was run over the period of 30 days. Over 10,000 isolates were exposed to these conditions — and they all died.
And in fact, these six surviving microbes actually did better under these conditions. Surprised by the result, the researchers took a closer look at the survivors, and following a genetic analysis concluded that they all came from the same genus: an extremely hardy extremophile called Carnobacterium.
Carnobacterium can be found in cold climates around the world, including Alaska and the oxygen-poor waters of Ace Lake in Antarctica.
Indeed, it's a startlingly common anaerobic organism that doesn't require oxygen for growth. And in fact, a species of Carnobacterium (CB1) is used as a food additive for vacuum or modified atmosphere-packaged ready-to-eat and processed meats. In other words, it's the kind of bacterium that could easily make its way onto a probe bound for the Martian surface.
As the researchers note in their study, "the ability of terrestrial microorganisms to grow in the near-surface environment of Mars is of importance to the search for life and protection of that planet from forward contamination by human and robotic exploration." Moving forward, and despite the fact that Mars has a highly irradiated surface, scientists will now have to ensure complete sterilization of all artifacts bound for the Martian surface.
The study was recently published in the Proceedings of the National Academy of Sciences.
Top image Randolph College. Other images: ID1974/shutterstock, NASA X 2.