Image courtesy of © Michael Studinger/
Lamont-Doherty Earth Observatory of
Columbia University
Many of the sounding flights passed near the Vostok base—when flying over the featureless landscape, pilots liked using the Soviet flagpole and radio mast to orient themselves—and the “water reflections” recorded there suggested the presence of a particularly large subglacial lake. But not much was made of all this; scientists at the time were less interested in water than in the ice thickness. “People chatted,” Priscu says. “No one took it seriously.”
Their chat turned more serious in 1994, when images from the European ERS-1 satellites were added to the earlier radio-echo soundings and even earlier seismic readings. What had been thought to be frozen sediment on the seismograms was pronounced to be water, and thus it was officially confirmed that beneath Vostok Station lies a huge lake, smaller in area than Lake Ontario but with more than three times the volume. Reviewing the surveys from all the sources, Martin Siegert—then a graduate student, now head of the school of geosciences at the University of Edinburgh—counted 76 lakes besides Vostok scattered around the continent. Also in the mid-1990s, another group of scientists proposed the now widely accepted mechanism for how lakes can form under glaciers: Heat radiating from Earth’s interior is trapped under the thick, insulating ice sheet, and pressure from the weight of all the ice above it lowers the melting point of the ice at the bottom.
The Soviets chose the site for Vostok Station because the ice there is thicker than anywhere else in the world—12,280 feet—and they needed thick ice. They planned to drill out ice cores to study past climates. Ice keeps a record of environmental changes as it accumulates over thousands of years, so the longer the core, the better. Soviet researchers also planned to keep the base operating year-round, even in the deep cold and dark of winter. In his account of the drilling, Russian physicist Igor A. Zotikov often invokes Murphy’s Law. Drills got stuck, pumps failed, boreholes closed. It took 30 years for the men to drill a borehole to the bottom of the ice. But over the years, first as Soviets, then as Russians, and sometimes with help from non-Russians, Zotikov and his colleagues extracted several useful ice cores, including a landmark one that held 420,000 years of climate data, through four full ice age cycles.
In 1998, while boring near the bottom of that long core, expecting to hit bedrock, the drillers brought up ice with crystals that were startlingly different from those usually found in glacial ice. The crystals were large, for one thing, some of them three feet long. Apparently the drillers had hit meltwater from the top of Lake Vostok that had slowly refrozen and accreted onto the bottom of the overlying glacial ice sheet. After taking out 275 feet of it, the Russians stopped drilling, leaving another 150 feet of ice as a barrier to the lake in case drill and fuel contaminants should leak downward. “We can think of the Vostok drill as a 65-ton enrichment culture,” says Brent Christner, a microbiologist at Louisiana State University. “I wouldn’t be surprised if there wasn’t a booger on it.”
The Russians shared samples of the accreted ice with their French and American collaborators, who came up with wildly contrasting findings. After removing the outside (presumably contaminated) parts of their samples, all the researchers cleaned and melted the (presumably uncontaminated) center ice and looked for signs of microbial life. Working in separate labs, Americans David M. Karl at the University of Hawaii at Honolulu and Priscu found strong signs; both detected hundreds, in some cases thousands, of bacterial cells per milliliter of ice. Some of the bacteria had intact membranes, so “they were alive fairly recently,” Priscu says. They concluded that Lake Vostok may support a viable population of microbes.
In contrast, Sergey Bulat, a molecular biologist at Petersburg Nuclear Physics Institute in Russia, and his French colleague Jean-Robert Petit, a glaciologist at the University of Grenoble (and lead author of the classic paper on the 420,000-year Vostok climate record), detected only a few cells per milliliter; in some specimens they found none at all. The ice was essentially “germ free.” One difference might have been in the samples: “It’s not like a mammoth bone where you saw it in half,” says Christner, a former student of Priscu’s. “Every centimeter of accreted ice represents a different zone of the lake.” More likely, the reason for the conflicting results was a difference in lab techniques. Resolution has to wait until biologists get hold of samples of the Lake Vostok water itself. There was one life-form that Petit and Bulat did consider a plausible lake resident: a thermophile, or heat-loving microbe. In the Vostok core sample, they found a DNA sequence related to a bacterium that thrives in hot springs, like those in Yellowstone Park. Hot spots under the cold of Lake Vostok, they suggested, could come from deep tectonic faults in its bed.
