Lake Ellsworth might be a better bet for microbe-hunters, because it offers fewer hiding places. At roughly 12 kilometers long by 3 kilometers wide, with a depth of around 150 meters, it is but a puddle compared with the vast Lake Vostok. Measuring about 250 kilometers long by 50 kilometers wide, Vostok ranks among the world’s largest freshwater bodies. Ellsworth is neatly settled in a subglacial valley near the continental divide, where the overlying ice moves at its slowest. At around −30 °C, ice at the site is also twice as ‘warm’ as the ice on the Vostok plateau in East Antarctica, and is thinner by almost a kilometer. All this will make Lake Ellsworth much easier to access and extensively sample than its prominent cousin, says Siegert.
Even if Ellsworth and Whillans turn out to be sterile, the exploration might provide clues about what constrains life on Earth and elsewhere in the Solar System. Siegert says that it would be a “phenomenal result” if the lakes were found to be devoid of life, because they offer everything that bacteria need — including liquid water and nutrients — and their water temperatures are just a few degrees below zero.
The UK team hopes to reach Ellsworth in a single three-day session, using a drill that will melt the ice with a high-pressure jet of water, heated to 90 °C. Once the borehole is finished, the team will have around 24 hours to deploy a water-sampling probe and a sediment corer before the hole refreezes.
The equipment, fastidiously prepared to make sure that it does not contaminate the lake with microbes from the surface, was approved last year by the parties to the Antarctic Treaty. Siegert reckons that drilling will consume some 60,000 liters of water, produced by melting snow at the site. The water will pass through a five-stage filtration system and then be treated with ultraviolet light to sterilize it. “The water we will use to melt into the lake is cleaner than the ice that naturally melts into the lake,” says Siegert. The 5-meter-long cylindrical titanium probe that will travel down the hole on the end of a tether, taking samples at different depths in the lake, was assembled in a clean room in Southampton, UK, and will be unwrapped from its sterilized bag only once it sits in the clean borehole.
The main challenge, says Siegert, will be to complete all sampling operations within the very short window of time. If things go badly, however, the team has enough fuel to reopen the hole by pumping in more hot water. If the probe gets lost or stuck, the researchers may drill a second hole and deploy a second set of sampling instruments. Indeed, they might do this anyway to get an extra round of sampling, potentially adding confidence to the scientific results, says Siegert.
If Lake Ellsworth does host life, it could be identified by the end of the year. But the exploration of Antarctica’s hidden lakes has just begun, says John Priscu, a glaciologist at Montana State University in Bozeman, who is overseeing the Lake Whillans foray. Data from more than just three sites are needed, he says, before scientists can hope to understand how the hidden lakes and rivers interact with the overlying ice sheet by lubricating its movement, for example. Studying more lakes could also reveal whether their discharges of minerals affect the chemistry and biological productivity of the Southern Ocean.
“We have come a long way since the time, not long ago, when people thought that Antarctica was but a benign block of ice,” says Priscu. “It makes me happy to see the excitement surrounding our science. But I’m afraid we know still less about Antarctica’s subglacial environments than we know about some places on Mars.”