An ancient living laboratory of our planet’s past in Antarctica may have provided a preview of what we can expect to find deep below the barren surface of Mars and in the ice-shrouded seas of Jupiter’s Europa. Two of the world’s leading experts on life at the lower temperature extremes, Buford Price of the University of California, Berkeley and Todd Sowers of Penn State observed that microbes colonizing life appear to have two levels of metabolism: a survival metabolism in which they remain alive but become dormant until exposed to nutrients or higher temperatures, or, a maintenance metabolism for steady sustained growth.
The team observed that some organisms in permafrost appear to have “protein repair enzymes that maintain active recycling of certain amino acids needed for cell repair for at least 30,000 years.” They added that the “extremely low expenditures of survival energy enable microbial communities in extreme environments to survive indefinitely.”
In the Antarctic’s ancient ice-bound Lake Vostok they reported that nitrifying bacteria with low but active metabolisms have been found encased in liquid veins at minus 40 degrees F for more than 140,000 years. And, it takes about 108 years for carbon to turn over in the cells.
They projected from their conclusions that life moving so slowly that it appears to be frozen, dormant, or undectable may survive in the cold, icy and “cosmically radioactive conditions of outer space.”
Applying the Lake Vsotok microbe discoveries to the possibilities of finding life on Mars or Europa, they concluded that “Our results disprove the view that the lowest temperature at which life is possible is minus 17 degrees C in an aqueous environment.”
Their data showed no evidence of a threshold in metabolic rate at temperatures down to minus 40 degrees C. Due to the structured water in its cytoplasm, a cell resists freezing and ionic impurities prevent freezing of veins in ice and permit transport of nutrients to, and products from, microbes.
Lake Vostok, believed to harbor ancient life that has been isolated from open exchange with the atmosphere for several million years, is the largest subglacial lake on Earth, discovered in 1996 by Russian and British scientists underneath the Russian station Vostok in Antarctica — one of 140 subglacial lakes located beneath the Antarctic ice-sheet. At 250km long and 50km wide, some 4000 meters underneath the surface ice, and could be one of the most important scientific finds of the last several decades.
No other natural lake environment on Earth has this much oxygen as Lake Vostok — an oligotrophic extreme environment, one that is supersaturated with oxygen, with oxygen levels 50 times higher than those typically found in ordinary freshwater lakes. The sheer weight of the continental icecap sitting on top of Lake Vostok is believed to contribute to the high oxygen concentration. Microbial organisms in Lake Vostok must be capable of overcoming very high oxygen stress, and may have had to evolve special adaptations, such as high concentrations of protective enzymes, in order to survive.
sources: dailygalaxy.com, berkeley.edu