Note that water that has a lot of dissolved chemicals has a lower freezing point, as does water under pressure. Of course, anti-freeze is used to lower the freezing point of water.
http://nsf.gov/news/news_summ.jsp?cntn_id=126161&org=NSF&from=news
November 30, 2012
Researchers funded by the National Science Foundation (NSF) describe in a new publication a viable community of bacteria that ekes out a living in a dark, salty and subfreezing environment beneath nearly 20 meters of ice in one of Antarctica's most isolated lakes.
The finding could have implications for the discovery of life in other extreme environments, including elsewhere in the solar system.
If, as the researchers postulate, the bacteria survive purely from chemical reactions, as opposed to drawing energy from the sun or other sources, "this gives us an entirely new framework for thinking of how life can be supported in cryo-ecosystems on Earth and in other icy worlds of the universe," said Alison Murray of Nevada's Desert Research Institute (DRI), the lead author on the paper.
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Lake Vida is the largest of several unique lakes found in the McMurdo Dry Valleys, an ice-free area of the continent.
Lake Vida contains no oxygen, is mostly frozen and possesses the highest nitrous-oxide levels of any natural body of water on Earth. A briny liquid that is approximately six times saltier than seawater percolates throughout the icy environment below a depth of 16 meters with an average temperature of minus 13.4 degrees Celsius (or 8 degrees Fahrenheit).
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Despite the very cold, dark and isolated nature of the habitat, the researchers report that the brine harbors a surprisingly diverse and abundant assemblage of bacteria that survive, unlike most life on the planet, without drawing energy, either directly or indirectly, from the sun. Previous studies of Lake Vida dating back to 1996 indicate that the brine has been isolated from outside influences for more than 3,000 years.
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Geochemical analyses suggest that chemical reactions between the brine and the underlying iron-rich sediments generate nitrous oxide and molecular hydrogen. The latter, in part, may provide the energy needed to support the brine's diverse microbial life.
"It's plausible that a life-supporting energy source exists solely from the chemical reaction between anoxic salt water and the rock," explained Fritsen, a systems microbial ecologist and research professor in DRI's Division of Earth and Ecosystem Sciences.
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