Selasa, 17 Januari 2012

Engineering in Antarctica



January 15, 2012-- Engineers with British Antarctic Survey have now made it possible to go where no human has gone before: three kilometers down through solid ice, to a buried lake that promises to reveal vital clues to past climate change -- and could harbor life-forms never known before.

Enduring whipping winds and temperatures of minus 35 degrees Celsius (not counting the wind chill), the engineers used powerful tractor-trains to transport nearly 70 metric tons of drilling equipment across Antarctica's ice, over deep snow and steep mountain passes, to one of the most remote and hostile locations on the planet.

The target of this grueling journey: a spot on the ice high above Lake Ellsworth, a mysterious and untouched pocket of liquid water deep inside the West Antarctic Ice Sheet.

Now that the equipment is in place, a research team will return in November to drill a three-kilometer borehole into Lake Ellsworth to collect water and sediment. If they succeed, Ellsworth will become the first of Antarctica's 387 known subglacial lakes to be measured and sampled directly..



A cargo plane carried the tractors and drilling equipment for the Lake Ellsworth mission as far as Union Glacier, a site in the Ellsworth Mountains that serves as the major hub for all scientific operations to Antarctica's remote interior.


To get the equipment from Union Glacier to the Lake Ellsworth drilling site, the engineers hitched powerful tractors to sledges and skis to haul the heavy blue containers containing the drilling equipment.

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Soft, deep snow and concrete-hard sastrugi snow forms slowed progress, but the tractor-train reached the Lake Ellsworth drilling site in three days.


Upon arrival, an engineer fits GPS locators at the corners of the equipment storage.

Windblown snow will partially bury the equipment over the coming Antarctic winter, making it otherwise difficult to find when the science team returns in November to start drilling. (Antarctic summers are too short to transport the equipment and accomplish the drilling in a single season.)

In the coming months, this precious cargo will endure wind chills reaching minus 70 degrees C and wind gusts up to 160 kilometers per hour.
Spectacular explosions of snow, like this one detonated at the Lake Ellsworth drilling site during a previous visit, helped scientists decipher the shape of the buried lake. Researchers set off the explosions and then use seismic equipment to record the sound waves reflecting off rock, ice, water and other materials within the ice.


Seismic studies have revealed that Lake Ellsworth is a long, narrow U-shaped lake approximately 12 kilometers by 3 kilometers. It is 150 meters deep at its deepest point and covers an area of 29 square kilometers.

Ellsworth and other subglacial lakes in Antarctica can persist in a liquid state because the overlying ice provides insulation for the heat rising up through the bedrock from the earth’s core, melting ice near the base of the ice sheet.

This melted water flows into hollows and valleys beneath the ice just as it does on the land surface to form lakes. The largest and most well known subglacial lake is Lake Vostok on East Antarctica, which Russian scientists have been trying to access, so far unsuccessfully.


Small planes can land safely at the Lake Ellsworth drilling site during the summer months. Getting people and basic supplies to the site in November will not take the extreme effort of delivering the drilling equipment. But that doesn't mean the work will be easy. The team will live in tents and work on location for about six weeks.


Researchers will use a stream of high-pressure hot water blasted from the end of this high-tech yellow hose to drill through the frozen ice sheet lying above the Lake Ellsworth. The hose is a continuous 3.4 kilometers (long enough to extend from the surface down into the buried lake) and strong enough to support its own weight and that of the drill nozzle.

Other equipment delivered by tractor-train included: (1) an industrial-sized boiler to heat 30,000 liters of hot water to 90 degrees C for the drill (2) 3 large surface tanks (each with a 5-meter diameter) to store water above freezing point in temperatures as low as minus 20 degrees C and (3) several large-scale generators to provide electrical power to the drill.

Through a borehole carved using hot-water drill, the team will lower a titanium probe to measure and sample the water, followed by a corer to extract sediment from the lake. They will have just 60 hours to collect water and sediment samples before the borehole re-freezes.

The hot water drill will use and recycle the existing ice on site for the drilling fluid, minimizing the potential for contamination of the lake. All equipment was designed and manufactured to meet space-industry standards for "clean" technology.


Soon the sun will set for the last time over the Lake Ellsworth drilling site, bringing several long weeks of darkness. The engineers and scientists will return with the light, ready to make history.

The waters of Lake Ellsworth have been cut of from all light for as long as half a million years. Also under high pressure all that time, the hidden lake may have evolved unusual forms of microbial life.

If such microbes turn out to exist, they could help explain how life managed to survive during global deep freezes of the Earth's distant past -- during the so-called Snowball Earth episodes, when most if not all of the planet was enshrouded in ice. And they might up the odds that life could have evolved in other extreme environments, such as the liquid water known to exist beneath the icy surface of Jupiter's moon Europa.

Now we just have to wait and see.


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