Microbes collected from surface sediments near Lost Hammer Spring, Canada, about 900 km south of the North Pole, could provide a model for the type of life forms that may have existed or still exist on Mars.
The extremely salty, very cold and almost oxygen-free environment beneath the permafrost of Lost Hammer Spring in the Canadian High Arctic is the one that most closely resembles parts of Mars. So if you want to learn more about the kinds of life forms that could have existed – or may still exist – on Mars, this is a good place to look. After much research under extremely difficult conditions, researchers at McGill University discovered microbes that had never been identified before. Moreover, by using state-of-the-art genomic techniques, they were able to better understand their metabolism. In a recent article by ISME, scientists demonstrate, for the first time, that microbial communities living in the Canadian High Arctic, under Mars-like conditions, can survive by eating and breathing simple inorganic compounds of a type that has been detected on Mars (as methane, sulphide, sulphate, carbon monoxide and carbon dioxide). This discovery is so compelling that samples from the surface sediments of Lost Hammer have been selected by the European Space Agency to test the life-detecting capabilities of the instruments they plan to use on the next ExoMars mission.
Developing a plan for life on Mars
Lost Hammer Spring, in Nunavut in the Canadian High Arctic, is one of the coldest and saltiest land springs discovered to date. The water that rises through 600 meters of permafrost to the surface is extremely salty (~24% salinity), perpetually at sub-zero temperatures (~ — 5°C) and contains almost no oxygen (<1ppm dissolved oxygen). Very high salt concentrations prevent the Lost Hammer Spring from freezing, thus maintaining a liquid water habitat even in sub-zero temperatures. These conditions are analogous to those found in parts of Mars, where extensive salt deposits and possible cold salt springs have been observed. And while previous studies have found evidence of microbes in this type of Mars-like environment, this is one of the few studies to find live and active microbes.
To better understand the kind of life forms that might exist on Mars, a McGill University research team, led by Lyle Whyte of the Department of Natural Resource Sciences, used cutting-edge genomics tools and single-cell microbiology methods. to identify and characterize a new, and more importantly, a microbial community active in this unique spring. Finding the microbes and then sequencing their DNA and mRNA was no easy task.
It takes an unusual life form to survive harsh conditions
“It took a few years of working with sediments before we could successfully detect active microbial communities,” says Elisse Magnuson, a PhD student in Whyte’s lab and first author of the paper. “The salinity of the environment interferes with both the extraction and sequencing of microbes, so when we were able to find evidence of active microbial communities, it was a very satisfying experience.”
The team isolated and sequenced DNA from the spring community, allowing them to reconstruct the genomes of around 110 microorganisms, most of which had never been seen before. These genomes allowed the team to determine how these creatures survive and thrive in this unique extreme environment, acting as blueprints for potential lifeforms in similar environments. Using mRNA sequencing, the team was able to identify active genes in the genomes and essentially identify some very unusual microbes actively metabolizing in the extreme spring environment.
No need for organic matter to sustain life
“The microbes we found and described at Lost Hammer Spring are surprising because, unlike other microorganisms, they don’t depend on organic matter or oxygen to live,” Whyte adds. “Instead, they survive by eating and breathing simple inorganic compounds such as methane, sulfides, sulfate, carbon monoxide, and carbon dioxide, all of which are found on Mars. They can also fix the carbon dioxide and nitrogen gases from the atmosphere, which makes them highly suited for both survival and thriving in very extreme environments on Earth and beyond.”
The next steps in the research will be to further cultivate and characterize the most abundant and active members of this strange microbial ecosystem, to better understand why and how they thrive in the very cold, salty mud of the Lost Hammer spring. The researchers hope that this, in turn, will aid in the interpretation of the exciting but enigmatic sulfur and carbon isotopes that were very recently obtained from NASA’s Curiosity Rover in the Gale Crater on Mars.
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