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| Lake Vida - one of the most remote lakes of Antarctica [PHOTO: NASA Ames/Chris McKay] |
Washington: In one of the most remote lakes of Antarctica, nearly 65
feet beneath the icy surface, scientists from NASA, the Desert Research
Institute (DRI) in Reno, Nev., the University of Illinois at Chicago, and nine
other institutions, have uncovered a community of bacteria. This discovery of
life existing in one of Earth's darkest, saltiest and coldest habitats is
significant because it helps increase our limited knowledge of how life can
sustain itself in these extreme environments on our own planet and beyond.
Lake Vida, the
largest of several unique lakes found in the McMurdo Dry Valleys, contains no
oxygen, is mostly frozen and possesses the highest nitrous oxide levels of any
natural water body on Earth. A briny liquid, which is approximately six times
saltier than seawater, percolates throughout the icy environment where the
average temperature is minus 8 degrees Fahrenheit. The international team of
scientists published their findings online Nov. 26, in the Proceedings of the
National Academy of Sciences Early Edition.
"This study
provides a window into one of the most unique ecosystems on Earth," said
Alison Murray, a molecular microbial ecologist and polar researcher at the DRI
and the report's lead author. "Our knowledge of geochemical and microbial
processes in lightless icy environments, especially at subzero temperatures,
has been mostly unknown up until now. This work expands our understanding of
the types of life that can survive in these isolated, cryoecosystems and how
different strategies may be used to exist in such challenging environments."
Despite the very
cold, dark and isolated nature of the habitat, the report finds the brine
harbors a surprisingly diverse and abundant variety of bacteria that survive
without a current source of energy from the sun. Previous studies of Lake Vida
dating back to 1996 indicate the brine and its inhabitants have been isolated
from outside influences for more than 3,000 years.
"This system is
probably the best analog we have for possible ecosystems in the subsurface
waters of Saturn's moon Enceladus and Jupiter's moon Europa," said Chris
McKay, a senior scientist and co-author of the paper at NASA's Ames Research
Center, Moffett Field, Calif.
Murray and her
co-authors and collaborators, including Peter Doran, the project's principal
investigator at the University of Illinois at Chicago, developed stringent
protocols and specialized equipment for their 2005 and 2010 field campaigns to
sample from the lake brine while avoiding contaminating the pristine ecosystem.
"The microbial
ecosystem discovered at Lake Vida expands our knowledge of environmental limits
for life and helps define new niches of habitability," said Adrian Ponce,
co-author from NASA's Jet Propulsion Laboratory, Pasadena, Calif., who
enumerated viable bacterial spore populations extracted from Lake Vida.
To sample unique
environments such as this, researchers must work under secure, sterile tents on
the lake's surface. The tents kept the site and equipment clean as researchers
drilled ice cores, collected samples of the salty brine residing in the lake
ice and assessed the chemical qualities of the water and its potential for
harboring and sustaining life.
Geochemical analyses
suggest 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.
Additional research
is under way to analyze the abiotic, chemical interactions between the Lake
Vida brine and its sediment, in addition to investigating the microbial
community by using different genome sequencing approaches. The results could
help explain the potential for life in other salty, cryogenic environments
beyond Earth, such as purported subsurface aquifers on Mars.