Lake Vostok ( , "east") is
the largest of more than 140 subglacial
lakes found under the surface of Antarctica
. It is located beneath Russia
's Vostok
Station
, 4,000 meters (13,000 ft) under the surface of the
central Antarctic ice sheet, within the
Australian Antarctic
Territory. It is 250 km long by 50 km wide at
its widest point, thus similar in size to Lake Ontario
, and is divided into two deep basins by a
ridge. The water over the ridge is about 200 m (650 ft)
deep, compared to roughly 400 m (1,300 ft) deep in the
northern basin and 800 m (2,600 ft) deep in the southern. Lake
Vostok covers an area of 15,690 km² (6,058 mi²). It has
an estimated volume of 5,400 km³ (1,300 cubic miles) and
consists of
fresh water. The average
depth is 344 m. In May 2005 an island was found in the center of
the lake.
Discovery
Radar imaging
Airborne ice-penetrating
radar data first
showed lakes beneath the Antarctic ice-sheet in the late 1960s and
early 1970s. The existence of Lake Vostok was first noted in 1973
by scientists of the
Scott Polar Research
Institute, but not named by them.
Russian and British
scientists delineated the lake in 1996 by
integrating a variety of data, including airborne ice-penetrating
radar imaging observations and spaceborne
radar altimetry. It has been
confirmed that the lake contains large amounts of liquid water
under the more than three-kilometer thick
icecap, promising to be the most unspoiled lake on
Earth.
Its
water is very old, with a mean residence
time in the order of one million years
(as compared with six years for Lake Ontario, which is typical for lakes of that
size).
Temperature
The average water temperature is around ; it
remains liquid below the normal
freezing point because of high pressure from
the weight of the ice above it.
Geothermal heat from the Earth's
interior warms the bottom of the lake. The ice sheet itself
insulates the lake from cold temperatures on the surface.
Ice core
Researchers working at Vostok
Station produced one of the world's longest ice cores in 1998. A joint Russian, French,
and U.S. team drilled and analyzed the core, which is long. Ice
samples from cores drilled close to the top of the lake have been
analyzed to be as old as 420,000 years, suggesting that the lake
has been sealed under the icecap for between 500,000 and more than
a million years. Drilling of the core was deliberately halted
roughly above the suspected boundary where the ice sheet and the
liquid waters of the lake are thought to meet. This was to prevent
contamination of the lake from the 60 ton column of
freon and aviation fuel Russian scientists filled it
with to prevent it from freezing over.
From this core, specifically from ice that is thought to have
formed from lake water freezing onto the base of the ice sheet,
evidence has been found, in the form of microbes, to suggest that
the lake water supports life. Scientists suggested that the lake
could possess a unique habitat for ancient bacteria with an
isolated microbial
gene pool containing
characteristics developed perhaps 500,000 years ago.
Environment
Ecosystems
Since Lake Vostok consists of two separate basins divided by a
ridge, it has been suggested that the chemical and biological
compositions of these two
ecosystems are
likely to be different.
Pressure and oxygen
Lake Vostok is an
oligotrophic extreme
environment, one that is
supersaturated with
oxygen, with oxygen levels 50 times higher than those
typically found in ordinary
freshwater
lakes on Earth. The sheer weight of the continental icecap sitting
on top of Lake Vostok is believed to contribute to the high oxygen
concentration. Besides dissolving in the water, oxygen and other
gases are trapped in a type of structure called
a
clathrate. In clathrate
structures, gases are enclosed in an icy cage and look like packed
snow. These structures form at the high-pressure depths of Lake
Vostok and would become unstable if brought to the surface.
Life
No other natural lake environment on Earth is as rich in oxygen and
it is speculated that any organisms inhabiting the lake would have
needed to evolve special adaptations to survive. These adaptations
to an oxygen-rich environment might include high concentrations of
protective
enzymes.
Due to the lake's similarity to the
Jupiter
moon
Europa and
Saturn's moon
Enceladus, any confirmation of life living
in Lake Vostok would strengthen the prospect for the possible
presence of life on Europa or Enceladus.
Tidal forces
In April
2005, German
, Russian, and
Japanese
researchers found that the
lake has tides. Depending on the
position of the
Sun and the
Moon, the surface of the lake rises between 1 and
2 cm. The researchers assume that the fluctuation of the lake
surface has a pumping effect that keeps the water circulating,
which would be necessary for the survival of
microorganisms if there are any.
Research
To probe,
without contamination, the waters of Lake Vostok for life, plans
were initiated in 2001 by the Jet Propulsion Laboratory
to start with a melter probe — the so-called
"cryobot" — which melts down through the ice
over Lake Vostok, unspooling a communications and power cable as it
goes. The cryobot carries with it a small submersible,
called a "hydrobot", which is deployed when the cryobot has melted
to the ice-water interface. The hydrobot then swims off and "looks
for life" with a camera and other instruments.
In January
2006, Robin Bell and Michael Studinger, Geophysical researchers
from Columbia University,
announced in Geophysical Research
Letters the discovery of two smaller lakes under the
icecap, named 90 Degrees
East
and Sovetskaya.
It is also suspected that the Antarctic
subglacial lakes may be connected by a
network of
subterranean rivers.
CPOM glaciologists Duncan
Wingham (University College
, London
) and Martin
Siegert (University of Bristol
, now University
of Edinburgh) published in Nature in 2006 that many of the
subglacial lakes of Antarctica are at least temporarily
interconnected. Because of varying water pressure in
individual lakes, large, sub-surface rivers may suddenly form and
then force large amounts of water through the solid ice.
See also
References
- Ice Explorer Conceived for Other Worlds Gets Arctic
Test
- Robot to Explore Buried Ice Lake
External links
Wikis
Quiz
Map
Search
