BOZEMAN, Mont.--When drilling through the ice of Antarctica's Lake Bonney in the 1980s, John Priscu and his team would utter expletives when reaching a depth of about six feet, or two meters.
On their way down to liquid water, which lay under a permanent ice layer about 15 feet deep, they invariably struck a layer of sediment.
"At first I cursed the sediment layer because it dulled the drill bits," recalled Priscu, a biologist at Montana State University-Bozeman who has done research in Antarctica for about 15 years.
Now he has kinder words for the pieces of sand and gravel entombed in the ice of Lake Bonney and several other lakes in the Antarctic Dry Valleys. That sediment layer, Priscu has learned, is alive. It supports a community of primitive microorganisms that know how to survive in an environment commonly associated with Popsicles.
Priscu, MSU civil engineer Ed Adams, postdoctoral student Chris Fritsen and six other scientists have written a paper on life in the Antarctic ice that appears June 26 in the journal Science. Days before the paper was to appear, Priscu, Fritsen and Adams were answering questions from reporters for the NBC Today Show, the BBC, Newsweek, the Washington Post, the New Scientist and several wire services.
Their work is analogous, Priscu and Fritsen said, to studies aimed at discovering life on Mars and Jupiter's moon Europa. Exobiology, or the search for life on other planets, is a hot topic now and is driving most of the public interest in discoveries like the one in Antarctica, the scientists said, although that focus is only a small part of their article.
Priscu admits it's hard to believe anything lives in the Antarctic Dry Valleys. It's a desiccated, rocky, desertlike landscape that looks like the surface of Mars except not as red. The air temperature is about that of a typical freezer.
"When [British explorer R.F.] Scott came walking down these valleys I'm sure he never thought there was something alive," Priscu said.
The key is liquid water. Adams figured out from trenching into the ice that the bits of gravel and sand in the sediment layer absorb sunlight during the Antarctic summer and create little pockets of water. The sediments, blown onto the lake by the wind and then buried, have bacteria and other microorganisms called cyanobacteria attached to them.
In the presence of liquid water and carbon dioxide from the surface, the cyanobacteria photosynthesize and produce organic carbon, which the bacteria use to make carbon dioxide for the cyanobacteria, and the cycle repeats itself.
"It's a lifecycle at the two meter level," said Adams. "It's a little ecosystem able to exist there."
What's more, this microbial community seems to make an ice-fixing substance--like antifreeze--that keeps the water pockets liquid for an extra two weeks before the onset of winter.
Fritsen said that's long enough for some of the microorganisms to reproduce. Some bacteria double every month, while others may take several years to double, he said.
"It's on the timeframe of lichens or cryptoendoliths--the microalgae that grow inside rocks in Antarctica because that's where the humidity is," he said. "It's very slow."
With three more years of funding from the National Science Foundation, the scientists plan to take a closer look at the lake's icy ecosystem.
"We want to know what organisms are doing well, how they do it, and how they can survive the freeze and thaw cycles in a liquid water environment," said Fritsen, who leaves soon for a faculty position at the University of Nevada at Reno. He'll take a portion of the new project, which he spearheaded, with him.
"We think we need to understand the interaction between organisms on our own planet to give us some signs of what to look for in other systems," Priscu said. "What we're saying is that for life on the edge you need a consortium of organisms to exist."
Other extreme environments where scientist have found life include hot vents along undersea trenches, deep in the earth's subsurface and in hot springs.
"Up to now people haven't looked in fresh water ice," Fritsen said. "They've looked in sea ice, and now scientists are talking about drilling into glaciers."
Priscu said the paper also says something about global climate change, which he studies in other projects.
"If this community reaches a steady state at two meters, then a change in meteorological activity will change the community," he said. "If it's too hot, the sediment will fall through the ice to the bottom. If it's too cold they won't get liquid water because there won't be enough radiant energy."
Journal
Science