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from NewScientist Website Downloaded from Scribd Website � �
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� � It took three weeks of crossing frozen terrain to reach the lake, and five days to punch a hole through its icy lid. � When they finally broke through to the water below, the excitement was palpable. Hands grabbed the gooey mud pulled up through the hole. � For this was no ordinary ice-fishing expedition:
The team's efforts - battling through 14-hour shifts in some of the harshest conditions on Earth - are part of a massive endeavor to uncover the continent's hidden secrets. �
Over a century ago, explorers trudged
across its white blanket in pursuit of world records, aware only of
the snow, ice and treacherous weather. � �
Hidden landscapes
active volcanoes,
hundreds of � � Their labor has revealed a pulsating continent with lakes, rivers, volcanoes, even life:
In a way, the adventure began in 1957, when a ship carrying members
of the third Soviet Antarctic expedition arrived at the East sledges
and a tractor but no men. � They had stumbled across a massive mountain range beneath, its peaks reaching up towards their feet (see picture far below). �
Almost 3000 meters high, the
Gamburtsev mountain range has an
Alpine topography, replete with rugged peaks and hanging valleys,
yet it is completely hidden from view. �
The Gamburtsev mountains, seen on a radar image through hundreds of metres of ice ANTARCTICA'S GAMBURTSEV PROVINCE PROJECT �
� These were the days before GPS and its Russian equivalent GLONASS, and pilots had to keep the Russian Vostok research station in their sights or risk getting lost over the vast, white, featureless expanse. � So it was pure luck that beneath the station sat the continent's biggest lake:
Vostok - like Antarctica's other large lakes - sits in a depression in the bedrock and is "inactive":
But in recent years, teams studying
other subglacial lakes have discovered a dynamic system of
streams and even rivers that interconnects some of them. � They concluded that water was flowing from one set of buried lakes to another.
At the last count, polar researchers have identified about 400 subglacial lakes in Antarctica (see map far below). The discovery has turned the image of a massive ice sheet grinding against the bedrock on its head. � Rather, there is an entire hydrological system between the ice and rock.
� "The temperature under the ice
was extremely hot - Yellowstone
hot" There's fire down there, too. � During the 2004-05 Antarctic summer, a joint US-UK team carried out an airborne survey to take radar, magnetometer and gravity measurements near Pine Island glacier in West Antarctica. �
They found something hundreds of meters
beneath the ice surface that strongly reflected their radar signal.
Hugh Corr and David Vaughan, also at
BAS, analyzed the findings and
concluded that the reflections were coming off a layer of ash and
rocks, the remnants of a massive volcanic eruption. � The explosion would have been on the scale of the 1980 blow-up of Mount St Helens in the US. Even today, the ice over Mount Casertz is depressed, suggesting heightened geothermal activity underneath. �
And in 2010 and 2011, seismometers
picked up the rumblings of another active volcano in West
Antarctica. �
In December 2012, an advance party of
tractors - each dragging a chain of shipping containers mounted on
sledges - had to cover the 800 kilometers separating the
McMurdo research station from the
lake. � The crew had to keep welding fractured metal, sometimes cutting parts from one container to patch up another.
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They had until the end of the month
before temperatures would begin to fall. In that time they had to
drill through 800 meters of ice to Lake Whillans, drop their
instruments through the hole one by one, take measurements, gather
samples, then pack everything up and head home.
One of the instruments dropped down the hole was a sensor to take the lake bed's temperature. � Until then, there had been only indirect hints that Antarctica's underbelly was warm.
Similar measurements have been taken at
some 35,000 sites around the planet. Only 100 or so are hotter than
the Whillans lake bed. � As an analogy, Tulaczyk points to the area between the Sierra Nevada mountains in the western US and Salt Lake City in Utah:
The West Antarctic ice sheet has grown and shrunk many times over the past few million years. � When the ice is thicker, it depresses the crust, which rebounds when the ice melts. As the crust bobs up and down, so does the viscous mantle 100 kilometers lower down. �
This constant massaging of the mantle
can release heat. �
They don't rely on energy from the sun,
not even in the indirect way that, say, fish at the bottom of the
ocean do when they eat dead material that falls from the surface. � Blood Falls is a salty waterfall, and salty water conducts electricity better than freshwater. So earlier this year, Mikucki and her team went out to the area with instruments that can remotely measure electrical conductivity beneath the ice. � �
� Blood Falls offers clues to how life survives beneath the ice USAP �
� � They found large pockets of high conductivity beneath the Taylor glacier. �
The researchers believe the sediments
there are saturated with brine and could host the microbial
ecosystems that flow out at Blood Falls. � Over the past decade Russian scientists have been drilling down to Lake Vostok. � The first time they broke through to it, in February 2012, the samples they brought back up to the surface were badly contaminated with the drilling fluid they used to keep the borehole open. �
After colleagues in Grenoble, France,
cleaned them to remove any trace of contaminants, the Russians found
no conclusive signs of microbial life. � Any search for life under these conditions is bound to be inconclusive.
She would also like to have water from the main body of the lake. � At the minute, they are only sampling the very top layer, which rises into the borehole during the final phase of drilling.
Tulaczyk and his colleagues did get a
sample of pristine water from Lake Whillans. Admittedly, their task was easier, with far less ice to get through and warmer temperatures to contend with. � They didn't need to keep the borehole open with drilling fluid. Instead, they used a hot-water drill - collecting boiling snow at the surface, irradiating it with UV light to kill everything inside, and then pumping it down through the ice. The nozzle and other equipment were also irradiated and washed with hydrogen peroxide. �
When the team broke through to Whillans
on 27 January 2013, it was the first clean drilling into a
subglacial lake, says Tulaczyk. In the water samples they found plenty of evidence for a thriving microbial ecosystem. � DNA sequences suggest that the microbes in Lake Whillans are chemoautotrophs, like the ones at Blood Falls.
On 8 January this year, the team drilled at another location, downstream of the lake. � This time the borehole went through the Ross ice shelf, just above the glacier's grounding zone, where the ice lifts off the bedrock and begins floating on ocean water. � The researchers lowered a camera down into what is essentially an estuary hidden beneath the ice. They found a lot more than microbes, netting shrimp-like amphipods and spying eel-like fish on their screens. � Powell wants to go back and trap them.
The big question is what supplies the energy for all this life. �
The ocean beneath the ice here is dark
and 800 kilometers from open water, so the sun is unlikely to be the
energy source. Could the entire food chain - all the way up to
amphipods and fish - rely on chemoautotrophic microbes? � Despite being devoid of sunlight, vent ecosystems sustain large animals like tube worms - and it all rests on bacteria that get their energy from chemicals spewing out of the vents. � Geothermal and volcanic activity beneath the West Antarctic ice sheet could supply energy for large organisms too, not just microbes.
� "Deep beneath the ice, they found fish and even
netted shrimp-like amphipods"
� Powell's team plans to lower a 7-metre-long remotely operated underwater vehicle, bristling with instruments, down a borehole to find out more.
It's not just about finding new life forms here on Earth. � Exploring subglacial Antarctica may boost efforts to look for life elsewhere in the solar system, such as on the frozen moons Europa and Enceladus. � Both harbor liquid water under their vast icy surfaces.
We have come a long way from the early days of Antarctic exploration. � Less than 150 years ago, geologists thought Antarctica's ice was anchored to the peaks of a volcanic archipelago. No one suspected it hid a continent, let alone life. � Our image of Earth's seventh continent has changed forever.
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