Seeking life in Vostok's deepest ice

Tubes of ice core from the Lake Vostok drill hole 5G, stored at the USGS NICL in Denver, Colorado.
Photo by Melanie Conner taken in October 2002 from the Antarctic Photo Library.

By Kristan Hutchison
Sun staff

[The article originally appeared on pages 1 and 10 of the November 3, 2002 issue of the Antarctic Sun.; it included the above photo. As this article appeared on portions of multiple pages of a PDF document, it was best shared in this form here. The companion article from the same issue, which describes the NICL, appears here. The original issue containing these articles appears here: http://antarcticsun.usap.gov/pastIssues/2002-2003/2002_11_03.pdf.]

Clear as diamonds and fragile as glass, the most carefully guarded cargo leaving Antarctica last year was 40 feet of ice core from Lake Vostok.

The 12-meter core wasn't the first shipment from the ancient, ice-capped lake, but it may be the most important, revealing what lies in the waters below.

"This ice is very precious and is the best template today of the chemical and biological content of the lake," wrote Jean Robert Petit, a senior scientist at the Laboratoire de Glaciologie et Geophysique de l'Environnement in Grenoble, France, where the ice now resides.

In 1998 the Russians drilled two miles (3.3 km) of ice from above Lake Vostok before halting a few hundred meters from the liquid lake water. When researchers began to look at the ice core, they realized the bottom of core was not the usual accumulated snowfall compressed into ice, but lake water that had frozen to the ice above as it slid over the lake. If anything lived in the lake it might be trapped in those final feet of ice core.

"The closer you can get down to the lake itself the stronger your argument is that that ice is truly represen- tative of what's in the lake," said John Priscu, a researcher at Montana State University. "That's why we're striving to get this real clear ice from the bottom; it is different physically."

The deepest Vostok ice core was left in a snow cave at Vostok Station until last season, when it was flown to McMurdo and then shipped in a freezer-box to Christchurch. There it was transferred to a commercial container ship, which carried it to Marseilles. The freezer box of core was loaded in a truck and driven to Grenoble.

"Since this ice is very precious, a considerable care has been taken and the National Science Foundation, Dave Bresnahan, supervised, organized and took care of each step of the transportation," wrote Petit. "The ice arrived in Grenoble in perfect state."

At an April conference at the National Science Foundation in Washington, D.C., the heads of science programs for America, France and Russia agreed to split the core equally between the three countries. They also set aside two segments of core, each a meter long, for further studies. A three-nation call for proposals to study the final two cores will be launched at the end of this year, Petit wrote.

"Nobody has a full core of Vostok," said Eric Cravens, curator at National Ice Core Lab in Denver, Colo., where about 700 meters of ice from early Vostok shipments is stored in silver tubes.

The U.S. received every third meter of the earlier shipments of Vostok ice, which came from higher up the core. In the freezer room, Cravens pulls out a two-foot piece of that ice and holds it to the light. The core is coated in a brown sheen from the kerosene the Russians used as a drilling fluid. It's like looking through a dirty window. The inside of the core itself is like glass. This particular piece is formed from about four crystals, Cravens said.

The Vostok cores in stock at the National Ice Core Lab go down to 11,913 feet (3,610 meters). "We have a little bit from the bottom, but not the super deep stuff," Cravens said.

The super-deep stuff remains in Grenoble, where the Russian and French scientists have started to select their samples and analyze it for signs of life.

"The analysis is very delicate and difficult, because the accreted ice is incredibly clean," Petit wrote. "Since the ice contains almost nothing, it is very difficult to prevent the contamination from our environment during analysis."

In Russia, Sergey Bulat and his colleagues are working with four segments of the super-deep accreted ice core from different depths at the Division of Molecular and Radiation Biophysics, Petersburg Nuclear Physics Institute. They have just started look- ing for bacteria in the new segments.

While the DNA work is done in Russia, the Russians and French are collaborating to decontaminate and meltwater process the samples using their own techniques in a "clean room" at the lab in Grenoble.

Those same techniques brought them results with earlier samples of accretion ice from further up the core. In that ice they found evidence of three bacteria which all were similar or related to those found in hot springs and hydrothermal vents. They also demonstrated the presence of many diverse bacterial contaminants, mostly from drilling fluid.

The Russian discovery is supported by French research and implies the lake may be warmed by geothermal activity.

"If this emerging picture is correct, Lake Vostok could harbor a unique assemblage of organisms fueled by chemical energy much like that observed in deep-sea vent systems," wrote Priscu. Priscu has also found microbes in the Vostok ice core, though of a different kind than the Russians. His research team received 16 Vostok ice core samples last year, including six from accreted ice further up the core. He and other American scientists are still waiting for sections of the deep Vostok core to be brought back to the U.S. Priscu requested 11 more samples of Vostok core, including some of the deepest accreted ice.

"It should have some unusual things in it, but they're probably down near the bottom," Priscu said.

The microbes Priscu and his colleagues found so far are garden-variety, similar to those found in the soil anywhere on Earth. He theorizes those microbes were carried in the air and trans- ported down to the lake water with the layers of snow.

The microbes may survive within the ice in a web of microscopic tunnels, believes Buford Price, a researcher at the University of California, Berkeley. He plans to test his theory using slices of the Vostok ice core.

Salt, acids and other chemicals in the atmosphere fall down with the snow and become part of the icesheet. As anyone who's sprinkled salt on an icy sidewalk knows, salt melts ice by lowering the freezing temperature. That's also why seawater takes longer to freeze than freshwater lakes.

The salts and acids in Antarctic ice act the same way, Price points out. Wherever three ice crystals meet, a salty or acidic solution collects in the threadlike crack, forming a permanent liquid channel. And where there's liquid water, life can exist, provided some nutrient is available. In this case, microbes in the channels can extract energy from the salt or acid.

"It's a hostile environment, these veins. They're filled with some harsh reagent that would poison a higher life form, but microbes that we know exist on Earth have learned to live in some extreme environments, whether hot or cold, salty or acidic or even devoid of oxygen," Price said.

Price will look at the frozen Vostok ice samples through a fluorescent microscope, hoping to see threads of microbes to confirm his theory. Based on studies of similarly cold environments in the ocean and soil, Price expects some or all of the microbes he finds in the ice will be in a nearly dormant state.

He'll try to revive some, placing thin slices of the ice on an agar medium with a sparse food source and leaving them at differing temperatures for several months. Some will be left in an atmosphere devoid of oxygen. If things work out as he predicts, the microbes will begin to revive and reproduce, leaving a grow- ing colony where each vein meets the agar medium. A match of the locations of the colonies with the exit points of the veins would be proof that the microbes had existed in the veins.

The discoveries of life in the Vostok ice core have changed Priscu's view of Antarctica's barren plains of ice. He found about 50 microbes per cubic centimeter of ice. Extrapolating that across the Antarctic continent, where the microbes could just as easily live, it's possible that Antarctic ice holds as much biological carbon as the world's unfrozen freshwater, Priscu wrote in an article titled "Earth's Icy Biosphere."

"Clearly, Antarctica contains an important global carbon reservoir that has been neglected by scientists in the past" Priscu said.

"When I would fly over Antarctica I used to look down and think ‘What a dead place,' but now I look down and think there's a lot of life in it."