Probing Antarctica’s pristine lake

Published: 27-Feb-2012

A sterile probe that will work in extreme conditions has been designed and built to drill through overlying ice into an under-ice lake in Antarctica to investigate the history of the West Antarctic Ice Sheet. All equipment must be sterile to ensure the samples are not contaminated and that no contamination is passed into the pristine lake.

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A project to survey an ancient and untouched lake under Antarctica’s ice sheet required engineers at the UK’s National Oceanography Centre to design a sterile probe that would work in extreme conditions.

A lake in Antarctica that is two miles under an ice sheet is where scientists will be looking for signs of life later this year. UK scientists and engineers aim to drill through overlying ice to sample its waters and recover sediment from the lake bed to investigate the history of the West Antarctic Ice Sheet. It is one of the biggest UK projects of exploration in recent years, involving teams from 10 of the UK’s top universities, research institutes and manufacturers.

Lake Ellsworth is one of several hundred under-ice lakes in Antarctica. These sub-glacial lakes are made of ice that is kept liquid by the geothermal warmth of the Antarctic bedrock and the pressure of ice above. The lakes have been in existence for around half a million years. Protecting this ancient environment from contamination, and the samples that come from it, is central to the project.

The mission’s aim is to look for life and leave the lake in pristine condition. A team at the National Oceanography Centre in Southampton is building the probe that will explore the lake. The 5.5m probe includes a small sediment core unit to take a sample from the lake floor and 24 titanium bottles that will each hold 100ml of water collected at different depths of the lake. Large volumes of lake water will also pass through filter systems that will collect any bacteria or deposits that may be present.

It is essential that the probe is sterile. The scientists must be confident that the biological material they find originates from the lake.

Dr Nefeli Tsaloglou is responsible for controlling microbial contamination. She said: “Titanium has been used extensively on the probe because it is easier to clean than other metals and soft materials, such as rubber, which may be porous. The engineers have designed the probe with hardly any recesses and surface detail to make it easier to clean. The hygiene levels we are working to are higher than in operating theatres for keyhole surgery.”

The probe is cleaned and assembled in an isolation tent. This sealed chamber fills with hydrogen peroxide vapour, provided by a Bioquell L-2 generator, destroying any last signs of microbial life.

At 5.5m long, the probe is too long to fit into a standard microbiological isolation tent. Engineer Robin Brown has constructed a specially extended unit that will accommodate the fully assembled probe. After cleaning and assembling, the probe will be packed into a sterile bag ready for shipping to Antarctica.

The probe has been specifically designed, developed and built by the National Oceanography Centre (NOC) team. One key element is that the water samples will be kept at the same pressure as when they were collected. On return to the UK, the bottles will be delivered – still under pressure – to the scientists involved in the analysis stage.

Engineers building the specially extended isolation tent that will accommodate the probe

Engineers building the specially extended isolation tent that will accommodate the probe

The probe will have to cope not only with the pressure at working depths of more than two miles (around 300 bar) but also at the immense pressure that will be exerted on the bottles when the retrieved water starts to freeze and expand on the journey to the surface and across Antarctica (around 2700 bar). Despite being made of Grade 5 titanium, the bottles are expected to bulge under the pressure of the frozen sample.

Hazardous journey

At the end of 2011, a team from the British Antarctic Survey successfully delivered the first pieces of equipment to the drill site on the West Antarctic Ice Sheet. They crossed 150 miles of snow and ice, negotiating the Ellsworth Mountains and crevasses during the journey.

The kit will over-winter on site until the end of 2012 – the austral summertime – when the scientists and engineers arrive to start accessing the lake.

The next stage for the NOC team in Southampton is to practise packaging and deploying the probe. It is one thing to do this in a warm lab, quite another task in freezing conditions. In Antarctica the team won’t be working completely outdoors; some of the time they will be in a specially customised container that will offer some protection from the elements. But low temperatures and heavy gloves will test their dexterity and patience.

For more information about the project visit: www.ellsworth.org.uk/.

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