ght here on our home planet. Astrobiologists study the unlikely life surviving in Earth’s most extreme environments — places so cold, so dry, or so bizarre that scientists once considered them uninhabitable. These environments are great analogues for extraterrestrial terrains.
Temperatures on Axel Heiberg get as low as –40°F, several degrees colder than Mars’s warm weather. On a warm day, Martian temperatures can reach a balmy –30°F. Mars was probably warmer at some point in its history, when the tilt of the planet was shifted so that the polar regions got more sunlight.
This overlap of temperatures makes Axel Heiberg a good place to learn about potential sources of water in Mars’s subzero environment. Water is an important piece in the puzzle of extraterrestrial life, since most life on Earth needs water in some form in order to survive.
To astrobiologists, Axel Heiberg’s perennial springs are some of the most interesting features on the islands. The springs come right out of the ground, about half an hour’s hike from the McGill Arctic Research Station. Some look like little streams flowing down the side of the hill, others look like seeps oozing up from below, and still others look like bubbling ponds. Don’t let the Jacuzzi effect fool you, though — the springs are actually quite cold. Fascinatingly, they stay liquid year-round, despite an average annual air temperature of 5°F. We found that each spring is unique — water temperatures and flow rates vary between individual springs.
Many springs in cold climates on Earth derive heat from volcanic activity underground. But on Axel Heiberg, a lack of observed magmatic activity makes it necessary to develop a new model. Our accumulating research indicates that the springs probably originate nearly half a mile underground.
Scientists who have been studying these springs since the 1980s suggest that the geothermal gradient alone is enough to raise the temperature of the water. Hydrostatic pressure from a nearby lake then forces the springs to flow upward through the permafrost, making their way to the surface through tube-like structures of gypsum, a salt composed of calcium sulfate. By the time the springs reach the air, they have picked up so much salt that they have three times the salinity of saltwater. The salt acts like an antifreeze, allowing the springs to stay liquid even when the weather is well below the normal freezing temperature of water.
Sources of liquid water may be the obvious places to look for life, but organisms can flourish even where water is perpetually frozen. I spent much of my time in the Arctic digging holes in the permafrost, collecting soil samples in a search for life.
Axel Heiberg may be harsh for most large life forms, save the occasional caribou or well-insulated Arctic hare. Look on a smaller scale, though, and you’ll find bacteria thriving in permafrost nearly a meter underground. Permafrost occurs on Mars, too, opening the doors for more analog studies.
On Earth, permafrost is characteristic of polar regions. It thaws during the summer, creating an “active layer” of soil. Dig through the layer of soft soil and you will eventually hit the solid, perfectly flat table of ice-cemented ground that exists in the Arctic and Antarctic. Analysis of our soil samples in laboratories back in the United States revealed the presence of metal-reducing and sulfur-reducing bacteria much like those found at the other end of the earth in Antarctic permafrost.
Frozen soil isn’t the only place on Axel Heiberg to find bacteria. Axel’s springs are another logical place to look for life — and indeed, the springs are surrounded by slimy layers of sulfur-reducing bacteria. Microorganisms even form colonies called endoliths inside giant chunks of rock or gypsum salt.
It seems as though life can find a niche no matter how unbelievable the environment. To me, a community of bacteria living where nothing else can is one of the most compelling scientific beauties I can imagine on Earth. I’d pick a barren, frozen desert over a teeming jungle any day, and Mars is the most