First Contact (5 page)

In 1998, even before many of the most dramatic extremophile finds were made, a prominent University of Georgia microbiologist named William “Barny” Whitman asserted in the
Proceedings of the National Academy of Sciences
that half or more of the biomass on Earth, the intact cells of creatures, plants, and single-cell organisms, lives thirty feet or more below the surface of the land and four inches or more below the bottom of the oceans. Since then, experts have debated the details of the estimate by Whitman and his colleagues, but have accepted the conclusion that of the life on Earth—the cells that make up all the insects, trees, mice, birds, fish, bacteria, and us—about half consists of those invisible to the eye, single-cell organisms that live below the ocean and below the ground.

Their conclusion, so at odds with how most of us understand the planet on which we live, will perhaps make this additional insight into the extremophile world more palatable: Researchers are also finding microbial life in the ice of the world's thickest and coldest glaciers, in the so-called cryosphere.

The presence of organisms near the top of a glacier, where sunlight can warm and liquefy the ice, seems to make sense, as does microbial life along the glacier's ever-moving bottom, where the Earth's geothermal warmth and the glacier's friction create a somewhat watery environment. But recent discoveries have included the presence of organisms, or organism remains, at almost any depth measurable. While the research isn't conclusive, it certainly appears that some are not in a dormant or spore phase, but
rather are actively metabolizing chemical impurities in the ice, using them as an energy source to maintain the disequilibrium needed for life and to repair their DNA, and to consequently live for impossibly long periods of time. This most extreme of ecosystems is apparently made possible by an unusual but universal property of glacial and sea ice: Those seemingly solid blocks actually contain a maze of minuscule veins that can include liquid water in ice to very low temperatures. This can happen because the physics of ice crystallization pushes all extraneous salts, minerals, and organisms into these microscopic pathways, creating environments where a microbe would have the nutrients and the unfrozen water needed to live. Some of the pioneering work in this field is being done in the unlikely and balmy setting of Baton Rouge, Louisiana.

On the day I visited Louisiana State University and its glacial life program, it was in the seventies outside. Students were mostly wearing shorts and T-shirts, and the world was green and soft. In the cold room where program director Brent Christner and his students do their work, the temperature was a steady 23 degrees Fahrenheit. We had on parkas and lots of polar fleece. Working in the icy cold has left at least one of the grad students perpetually chilled and wearing a down parka as he walks around campus.

The two-hundred-square-foot cold room is for studying the ice and houses a workstation with high-precision air quality control, a light box, a band saw, a subzero growth incubator, and an air vent—under which the “windchill factor” drops even further. But the real treasure trove is through another thick, tightly latched door into a –20-degrees storeroom filled with ice cores and ice blocks from around the world, and especially from Antarctica. Wrapped in heavy-duty plastic bags and stored in see-through container boxes from Home Depot, the ice looks as lifeless and exciting as cement. But Christner knows better; years of work have shown that they contain microorganisms barely eking out a living, yet apparently metabolizing, using energy, maintaining their DNA and splitting—all at a, well, glacial pace. Christner is confident this is correct because he has observed microbes that have been frozen in ice for many thousands of years start
wiggling when warmed up a bit in the lab. Working with Mark Skidmore of Montana State University, Christner and his team, the Interdisciplinary Collaboration Investigating Biological Activity in a Subglacial Environment (ICIBASE), are finding recently unimaginable activity at the icy boundaries of life.

Christner has made five trips to Antarctica between 2000 and 2009 searching for life in ice. Scientists like Christner especially love the McMurdo Dry Valleys of Antarctica because of its many extremes: It's a two-thousand-square-mile region of snowless, gravelly valleys on a continent otherwise covered in white, it has liquid lakes hidden beneath deep coatings of ice, scores of glaciers, and winds of up to two hundred miles per hour. Not that long ago, the region was considered to be devoid of life. Now teams go down looking for, and finding, all kinds of microscopic organisms. It's also a mecca for scientists and engineers preparing for the day when Americans (or others) will need to know how to operate, and what to look for, in the environments likely to be found on Mars and elsewhere beyond Earth. Just a few miles from the ICIBASE camp, a NASA-sponsored team was continuing its long-term research with technology they hope will one day travel to Jupiter's moon Europa and be used to explore the enormous liquid ocean known to lie beneath its thick crust of ice and suspected to have conditions suitable for life.

Making the LSU research station anywhere near as frigid as where the ice came from requires heavy-duty condensers, compressors, and fans and results in a constant hissing sound—adding to an already surreal disconnect between inside the room and out. It's a small place that combines the feel of an operating theater and a meat locker, minus the hanging carcasses. Here ice is the star.

An ICIBASE alumnus hauled out three thirty-pound blocks from the storage room, each from a different part of McMurdo's Taylor Glacier, and placed them on a light box. One was clear, though full of captured, cartoonish bubbles; another had thin layers of sediment that produced an elegant, soft layered effect that could have come from a potter's hand. The last
sample came from the bottom, where the glacier—a river of ice—grinds the rock below and mixes with it. Christner was most interested in the second sample, the one with the thin layers of sediment.

“We can melt the ice and bring the microbes out—they're alive, we know this,” he said, gesturing to the block on the light box. “We can also take a natural ice sample from Taylor Glacier and measure the gas concentrations, and I can tell you in a piece of ice like this they make no sense at all. The level of CO
₂
is [three thousand] times what it is in the atmosphere now, so something caused it to increase. That value couldn't possibly be atmospheric from earlier days because it's way too high. Oxygen is normally twenty percent of the total gas in ice, exactly like in the atmosphere. But in this area of our sample, the O
₂
depleted. So you have CO
₂
increasing and oxygen decreasing—it's a classic signature cellular respiration.”

Okay, the microbes may be respiring (breathing, if you will) in the ice, but how could they possibly reproduce and keep their community from disappearing? That takes far more activity than these organisms could seemingly muster in their barely liquid, very salty ice vein habitats. Christner had an answer, one based on measurements of the rate at which microbes, living in ice at 5 degrees Fahrenheit, can build the genes needed to successfully divide and create a new organism. “There's a misunderstanding about microbes, that they're always dividing. But like humans, they're not reproducing all the time at all in nature. Okay, these guys are extreme—they may divide once in two hundred years. Just do the math: We know that some cold-adapted bacteria can synthesize about one hundred base pairs of DNA per day. But they have a genome with about three million base pairs, so it takes a while—not the kind of project a grad student would want to start up and ever expect to finish. Time means nothing to microbes. It's all about maintenance, just keeping alive.”

When ice from the latest expedition arrives, the room will have more than 1,500 kilograms of ice that could contain something on the order of 15 billion microbes—all in some stage of “living,” but nonetheless frozen in ice.

Pulling that precious ice from deep inside the Taylor Glacier was quite an operation, one that required two years of planning, a fair amount of equipment, and the help of National Science Foundation helicopters. It was frigid and windy when the team arrived at their site, nearby Lake Bonney, and set up camp. Each day they hiked a mile up to the face of the glacier and got to work. Using chain saws, demolition hammers, and ice picks, the group had to first build an ice stairway up about thirty feet from the base of the glacier. Then, over a week, they dug a tunnel more than forty feet into the ice—pulling out more than fifty tons via banana sleds. Above the tunnel was another hundred feet of ice, and picking the wrong spot to dig could lead to a catastrophic cave-in. That's why Christner and Skidmore helicoptered out from the American base at McMurdo Station and spent four hours intently surveying the glacier's ice face, looking for a spot without any telltale signs of surface weakness or calving.

The ICIBASE team—five men and two women—took turns with the equipment, each cutting and drilling until they were coated in ice chips and dust, and looking rather crazed. But the chain saw work was generally considered plum, because inside the glacier they were protected from the cutting winds that froze the haulers and lookouts on guard for teammates in distress, with windchill temperatures down to –40 Fahrenheit. At the end of their ice alley, the team studied the frozen walls for unusual and differing traits, and cut and drilled and yanked out slabs of up to one hundred pounds, for transport back to Louisiana and Montana for study. Two years before, they'd had to donkey-haul their catch out of the tunnel and through a boot-grabbing mudslide because the glacier had begun its yearly melt early, and a waist-high river had quickly formed between their ice castle and dry ground. This year they arrived sooner so they could finish the tunnel and airlift out the blocks before the melt river appeared.

The goal of the mission was to determine whether microbes in the ice constitute an archive of dead or metabolically inactive organisms, or if they formed a living, interacting community. Previous work in Antarctica had identified seemingly active biochemistry—the presence of by-product
carbon dioxide and nitrous oxide with distinctively life-produced signatures, akin to the gases ICIBASE had found in the Taylor Glacier ice—and raised the prospect of finding microbes with clearly identifiable forms and functions. In other words, Christner and a handful of others are working to prove the hypothesis that Antarctic ice, as well as glacial ice elsewhere, is not lifeless and unchanging but rather an ecosystem no different from a forest or stream. It's clearly an extreme, slow-moving, and spare environment, but it's a world that supports certain kinds of similarly constructed life just the same—organisms with the kind of antifreeze found in some cold-water fish, organisms that appear to depend on the biochemistry performed by other nearby organisms for their survival, organisms with an ability to withstand extreme desiccation and intense radiation. That trait is essential, since scientists assume they initially blew down to Antarctica from the oceans or other continents, withstanding long, harsh periods in the atmosphere. The definitive research has not been done yet that would prove glacial microbes are conducting the work of “life” in the ice—as opposed to what they do when they're brought into the lab, fed, and warmed up a bit, and begin to move around—but the logic of the argument is getting stronger with each expedition.

And how extreme can their Antarctic living conditions get? Russian and American researchers, including Christner, have identified signs of life almost three miles below the surface in ice that originates from liquid Lake Vostok, the largest of the recently discovered subglacial lakes on the continent. That's nearing halfway up Mount Everest if you're going in the other direction. A high, windswept plateau of East Antarctica, the surface of Vostok is often described as the coldest place on Earth. The irony is that the deeper the drill goes into the ice above Lake Vostok, the more likely that they'll find living microbes. The reason is that it gets warmer deep down in the glacier, and finally warm enough under the ice that Lake Vostok (roughly the size of Lake Ontario) stays liquid all the time. The weight and pressure of the glacier clearly are part of the reason why, but Russian scientists—who have worked at Vostok since the mid-1950s—believe
geothermal hot spots under the lake may be spitting out heat and gases as well.

Russian scientists and engineers are scheduled to make their long-delayed piercing of the pristine lake in 2011, bringing up what will be the first Vostok water ever touched by humans. Astrobiologists and Antarctica specialists are torn—eager to know what might be living in the waters, but worried that the Russian drill and collection device will contaminate the lake. While Vostok is the largest subglacial lake in Antarctica, there are hundreds of others. One of them, Lake Bonney in West Antarctica, has already been explored and mapped by a NASA-sponsored mission headed by Peter Doran of the University of Illinois in Chicago and underwater-robot maker Bill Stone, one of the breed of out-of-the-box engineers drawn to the same challenges and questions as Christner and other scientists. Without men like Stone to design, calibrate, and operate robots and machines that allow scientists to make finds in the most inhospitable parts of Earth, the most revelatory astrobiology expeditions would never have gotten off the ground.

Tall and lanky, Stone is a grown-up version of the science geek who had a better chemistry lab in his basement than his high school did. When he was still in school, his mom suggested he join a club to meet other kids. Not knowing what it was, he chose spelunking. Some decades later he is still a caver, leading extreme expeditions into the deepest caves on Earth: weeks of rappelling into the dark, swimming through narrow water tunnels, sleeping well below the surface on ledges and outcrops sometimes never before visited, and then climbing back up sheer cliffs. When not caving, Stone runs Stone Aerospace outside Austin, where the Lake Bonney robot was conceived and assembled.