When the first images from the Mars Orbiter Camera, part of the Mars Global Surveyor Mission, were viewed by scientists they were impressed by the deep gullies cutting into the Martian surface and began to theorize as to the conditions that had formed them. The current and most popular theory is that the gullies were formed by underground water which had surfaced to run down sloping terrain, washing away the soil. With the presence of water being a prerequisite for developing and sustaining life as we know it, the discovery led to the question of whether the planet had ever supported life.
An explanation of how a cold, dry environment could support life was becoming necessary. To collect data on such a unique environment, scientists traveled to the Earth’s polesconsidered to be the most Martian-like conditions to be found on this planet. Studying the water sources in polar regions such as the Axel Heiberg Island in the Canadian High Arctic and the McMurdo Dry Valleys of Antarctica would make it possible to understand how water can exist in such extreme conditions, where temperatures vary from 5 to -22 degrees Fahrenheit, with desert-like rainfall totals.
During most of the year, Axel Heiberg Island is just 5 degrees F., maintaining a constant permafrost almost a half-mile down. Two of the island’s springs were found to have water originating equally from glacier and lake water with a salinity five times that of sea water. The spring water was discovered to be flowing through permeable salt beds underlying the water sources. Although the groundwater temperature was freezing, it continued to flow underground to a depth of nearly half a mile, warmed by the Earth’s internal heat up to 40 degrees F. The water moved fast enough to reach the surface with out the temperature changing appreciably, and the springs flow year around with little temperature fluctuation.
The conditions most like those on Mars are found on Antarctica in the McMurdo Dry Valleys, the continent’s largest ice-free area. Large lakes in this region are fed by melting glaciers in summer, when temperatures reach only a few degrees above freezing. Yearly moisture, usually in the form of snow, measures less than one inch. Even in the presence of these conditions, water is cycled into a large ice-covered lake which supports microbes on the lake bottom, the liquid water, as well as in the ice cover.
Models of life in such extreme Earth environments have been applied to various Mars features, such as the Gusev Crater, possibly a former ice-covered lake, and the Chryse region, using a dry valley model. Scientists believe that extreme habitats on Earth which support life could indicate similar Martian environments of the past might also have sustained life, evidence of which could be preserved in sediments and other traces left behind by those features.
