The fast track to the moons of Jupiter - and the key to life on Earth - is a prehistoric lake nearly three miles beneath the Antarctic ice cap.
To imagine Lake Vostok, you must first envision a great lake in a living landscape, a week's walk from end to end, too wide to see across from the highest hills on its flanks. Now simplify, subtract. Erase the surrounding woods and fields; hide the encircling hills. Remove the changing seasons and the replenishing rain. Still the winds that drive the waves; silence the beaches that soften the shores. Take out the fish; take out the weeds. Finally, shut out the sky itself; turn a surface of blue reflection to one of dark constraint. Leave only the waters, the minerals, the muddy depths. Then trap them, squeeze them, estrange them from everything that lives and dies elsewhere. From your creation emerges a simple world, a world that hungers for more.
About 150 miles long and 31 miles across, Lake Vostok is elongated in shape, much like eastern Africa's Lake Malawi or Siberia's Lake Baikal. In area (5,400 square miles), it's nearly the size of Lake Ladoga, the greatest of Russia's western lakes. Its volume (2,900 cubic miles) is a good match for Lake Superior's. Its maximum depth (1,800 feet) is similar to Lake Tahoe's.
These proportions place Vostok comfortably among the world's 15 largest lakes - but its setting is utterly singular. Lake Vostok sits beneath 2.5 miles of solid ice, close to the center of East Antarctica. If it ever had a direct link with the air above it, that connection ended some 30 million years ago. Climatologists at the ragged Russian base near Vostok's southern end - three hours by plane from the South Pole - have recorded the coldest temperature ever measured on Earth's surface: minus 128.6 degrees Fahrenheit, nearly cold enough to freeze carbon dioxide out of thin air. The only visible rocks within 600 miles are shooting stars fallen to Earth, rare black pebbles in the icescape.
Lake Vostok's forbidding remoteness makes it supremely hard to reach, and therefore unbearably attractive to scientists. Vostok's very isolation means it holds secrets no other place on the planet can. Its sediments contain a unique record of Antarctica's climate before the ice caps arrived - one that could revolutionize the science of the frozen continent. There could be prehistoric life in its waters, an indigenous ecosystem surviving with few resources - no sunlight, the tiniest of fresh-food inputs - and spurring adaptations never seen before. Were Lake Vostok open to the rest of the world, its faint records and fragile life-forms would have been overwritten long ago. But being cut off may have preserved them from the changes that endlessly erode and re-create the world above.
Vostok's existence was unknown until 30 years ago, when radar and seismographs allowed scientists to piece together a map. The first hints of water under the ice were detected in the 1970s; much later, in the early 1990s, satellites and data from earlier seismic surveys revealed Lake Vostok's full extent. In 1995, a borehole was drilled from Russia's Vostok station, named for the ship sailed by 19th-century Russian explorer Fabian Gottlieb von Bellingshausen and built in that godforsaken spot, quite by chance, long before anyone suspected something important might be below. The borehole came within 400 feet of entering the lake, but the drillers stopped short of breaking through to the waters beneath.
In the near future, however, millions of years of isolation may come to an end: Researchers from America, Britain, Europe, New Zealand, and Russia have started lobbying their governments for a multimillion-dollar, long-term effort to fathom Vostok's depths. Funding, for the most part, would come from the National Science Foundation in the US, the Natural Environment Research Council in the UK, and various other European organizations working together under the Scientific Committee on Antarctic Research (SCAR), the international body that oversees science in the southernmost continent under the terms of the Antarctic Treaty.
If the multinational teams of scientists get their way, the exploration of Lake Vostok - perhaps the most ambitious and complex scientific undertaking Antarctica has yet seen - could begin in less than five years. New bases will be built, some temporary, some permanent; new logistical infrastructures will be created to serve them; specially engineered drills will bore holes in the ice with blasts of hot water; and fleets of aircraft will transport thousands of gallons of fuel oil. (It takes a hellish amount of energy to get through 2.5 miles of ice.) Tele-operated and autonomous deep-diving robots will launch themselves from the boreholes into the great lake's waters, then sink through the blackness to the silent ooze below.
Glaciologists, sedimentologists, biologists, geochemists, and climatologists will try to understand how the lake waters circulate, where they come from, and where they go. They'll look for prehistoric life-forms and search for nutrient sources. They'll hunt for clues to how long the lake has been there, and what came before it. Long-dark Vostok will be pried open for inspection - a process that, however carefully undertaken, runs the risk of changing the lake forever and destroying what has made it unique.
Why take that chance? Some believe Vostok should be left alone because exploration might permanently damage its pristine ecosystem. But proponents of drilling believe Vostok could provide new insights into the young Earth's spectacular ecological crises, during which the whole planet was frozen solid, its oceans reduced to the very brink of lifelessness. And it could illuminate the possibilities of life farther off - in a vast ocean on Europa, Jupiter's fourth-largest moon, 483 million miles from the sun. Along with Mars, Europa is the most likely prospect for evidence of life beyond Earth, and Vostok is the closest thing to a Europan environment our planet has to offer. Isolated from light, warmed only from below, starved of nutrients, the life-forms of Vostok could teach scientists how life might persist in Europa's frigid climate, where temperatures average minus 250 degrees Fahrenheit. It would certainly show them how to look for it there: Exploring Vostok would be the nearest thing to a space mission without leaving the planet.
It's no surprise, then, that at NASA's Jet Propulsion Laboratory in Pasadena, California, the probes that will look for life in these icy depths millions of miles apart are being developed side by side. At Caltech and JPL, which designs and operates most of NASA's planetary spacecraft, a team of six engineers is adapting instruments, first developed to explore the hot depths of ocean-floor volcanic vents, for use in the isolated waters of Vostok or in Europa's alien oceans. The team is trying to develop a small metal probe - a cryobot (cryo means "ice" in Greek) - that can emit chemicals to create a sterile zone around itself, burrow through the ice using a high-pressure jet of hot water to clear its path, take samples, and transmit collected data back to the surface. It's also devising ways for the probe to see, retrofitting deep-water cameras to squeeze through a narrow borehole in the ice and still function in conditions of extreme pressure and cold.
But it's not just the technology that links Vostok and Europa. It's the ideas - pure, powerful ideas - that take scientists from the everyday world to somewhere far stranger, more abstract. In Lake Vostok's dark waters, they hope for visions from halfway across the solar system, and halfway back to Earth's beginnings.
"The lake - isolated for several million years - could contain microbes that have evolved in a manner unique to this environment," says Martin Siegert, a University of Bristol glaciologist who worked on the early satellite research that first exposed Vostok. "In effect, the lake can be thought of as a laboratory for investigating evolution."
Everything runs down. Hot baths get cold; fires turn to ash. The heat of Earth's core is slowly leaking out to space. In Antarctica, though, this heat loss is stymied by an insulating barrier: an ice sheet weighing billions of tons. The top of the ice is very cold indeed. The bottom, gently heated from below, is in some places warm enough to melt and collect as liquid water in pools or lakes.
In the 1970s, American, British, and Danish researchers used 60-MHz airborne radar to hunt for such hidden water pockets in Antarctica. Because radio waves can travel through ice, signals from the radar bounced off not the ice sheet's top, but its bottom. In some places, radio waves reflected evenly, suggesting that the ice was sitting on something much smoother than craggy bedrock. The obvious explanation was a layer of water. In 1974, the multinational team identified the longest stretch of subglacial water ever seen, near the Soviet Union's Vostok base. It was the first glimpse of the lake.
Few found the discovery very exciting. "Nobody talked about bodies of water under the ice - nobody thought about them," says Cynan Ellis-Evans, a microbiologist with the British Antarctic Survey (BAS). "Everyone had this mental picture of the water being just a few tens of meters thick." But in 1991, Jeff Ridley, a remote-sensing specialist with the Mullard Space Science Laboratory at University College London, directed a European satellite called ERS-1 (the first long-duration civilian radar) to turn its high-frequency array toward the center of the Antarctic ice cap. It confirmed the 1974 discovery: a flat plain at 105 degrees east by 77 degrees south - a glacial dimple nearly 150 miles long, with Vostok station at the southern end.
When Siegert put this new satellite imagery together with the airborne-radar readouts and older Soviet seismic charts, the vast lake was revealed in all its glory. "It was a eureka moment," says Siegert. Although Siegert had cataloged evidence for some 70 subglacial lakes, Vostok was by far the largest and most contained. "The data couldn't be interpreted as anything except a deep body of water," he says. And, purely by chance, other scientists had already drilled most of the way down to it. They weren't interested in the lake - they didn't know it was there - but instead were extracting and studying ice cores from the glacier above.
The ice below Vostok station is a history book, with each core a vertical record of prevalent conditions at a particular point in time: the amount of dust in the atmosphere, the levels of trace gases, even the weights of the water molecules themselves, which provide hints to major climatic events. The ice cores scientists had been pulling up told the story of four 100,000-year cycles, a century of the world's climate in each yard.
The Russians started drilling into this record in the 1970s, the French joined them in the early '80s, and the Americans signed up in 1989. By the time Siegert and his colleagues could confirm the lake's existence, almost 2 miles of ice had been hauled out of the glacier above, split into several slices, sampled, and shipped off to American, French, and Russian labs around the world. The scientists realized that if this routine continued, and drilling went on unchecked, they'd pierce the last level of ice and tap into Lake Vostok within a matter of months.
When Ridley made his findings public in 1993 in theJournal of Glaciology, he immediately roused scientific interest, moving SCAR to suggest that a workshop be held to decide if continued drilling made sense. In May 1995, two dozen researchers gathered to discuss this question at the Scott Polar Research Institute in Cambridge, England - the same institute where the original radar work was masterminded. "The US, France, and Russia - the three nations involved in the drilling - asked SCAR to come up with a recommendation regarding Vostok, and were willing to accept the outcome as being for the greater good," Ellis-Evans recalls. In other words, if anyone was going to drill into Vostok, the committee had to give the green light.
News of the meeting made its way to Ellis-Evans at BAS headquarters on the other side of town. As a biologist studying Antarctica, Ellis-Evans already knew that its surface lakes mattered, but like most of the world, he had no idea that the subsurface Lake Vostok even existed. "Frozen surface lakes of the Antarctic continent are an oasis," he says, "sitting in a Martian-like landscape, teeming with life." That life is mostly in the form of photosynthesizing microbial mats on the lake beds. Freed from predators by Antarctica's isolation, these mats leach nutrients from the "gin-clear" water, says Ellis-Evans, and create a stratified microbial ecology in the sediments below.
But there weren't going to be any photosynthesizing mats in Vostok's darkness 2.5 miles down. The water would be colder than in the shallow surface lakes, and the pressure immense. That didn't mean there could be no life. Assuming Vostok had once been a surface lake before ice covered the continent, organisms from that ecosystem might have found a way to survive. If that were the case, scientists would be looking at the ultimate biological time capsule - one that dates back 30 million years. The organisms' origins - and their adaptations to a weird world of cold, dark scarcity - made them the most tempting of targets for study.
"What the glaciologists wanted to do at the time was get as long a climate record as possible," says Ellis-Evans. "Another few hundred meters could have given them another glacial cycle. But that would mean drilling down to the lake. They wanted to know if the rest of the Antarctic science community had a problem with that. We told them that the more we heard about this, the more concerned we were about it. And we outlined the possibilities for life. As we had our say, we could see they were changing their views - they saw that they could damage the biology irreparably."
The potential problem Ellis-Evans describes is quite simple: The pressure at the bottom of the ice sheet would squeeze any borehole shut unless it was filled with a nonfreezing fluid - in practice, dirty kerosene. Putting a borehole like that through the ice and into the lake would create a miniatureExxon Valdez, releasing toxic fluids in what could well be one of the most delicate, perfectly preserved ecosystems on Earth.
At the close of the three-day meeting in Cambridge, SCAR agreed that Lake Vostok should be given special protection, and the American/French/Russian team was asked to halt drilling within 400 feet of the lake's surface. "A country could go against SCAR," says Ellis-Evans, "but most nations work within the essentially apolitical organization and accept its ground rules." So far, the agreement has been honored. During the meeting, it became clear that SCAR's interest in protecting Vostok and the life it might harbor was another reason to study the lake further by less polluting means.
Shortly after the Cambridge mandate, Antarctic Treaty countries signed a multinational agreement to further protect the vulnerable continent. "Any work in Antarctica now has a firm legal requirement to recognize and address environmental concerns," says Ellis-Evans. But even with the new legislation, the science of Lake Vostok continued to be a strange dance between the desire to protect and the desire to study. As researchers became more intrigued with the lake, their conflicting desires to either save or spoil it were slowly being pulled together.
When the size of Lake Vostok - and the possibility of ancient life within it - dawned on the wider world, the excitement began to spread. "I'd pretty much ignored it until two years ago," says Robin Bell, a geologist at Columbia University's Lamont-Doherty Earth Observatory who supports a Vostok drilling mission. "I couldn't see why it was important. And then I realized that it's a leaping-off point for a geological understanding of East Antarctica. As unique geologic structures are identified, the biological questions of survival in a hostile environment will follow - the geology is, in essence, the cradle in which life can form. Vostok," she adds, "could be linked to an understanding of life on Earth millions of years ago and to the potential for life beyond Earth."
In 1998, scientists arranged further meetings - first in St. Petersburg, Russia, then in Washington, DC - to discuss the lake, and whether it was worth going to at all. Last fall, members of the growing Lake Vostok community returned to Cambridge to try to pull together a definitive statement about Vostok's scientific value. Such a declaration is essential if SCAR is to set up a formal Vostok committee, itself necessary to convince the American, European, and Russian governments that it's worth spending millions of dollars to fund a multinational exploration of the lake.
The conference was held on a rainy Sunday morning at the end of September, with 60 established experts and young hopefuls crammed into a meeting room at Cambridge University's Lucy Cavendish College. Among those on hand was Peter Barrett, a tall, soft-spoken New Zealander who is trying to pinpoint the onset date of Antarctica's glaciation; Gordon de Quincey Robin, a short, round Brit who pulled together the radar surveys showing the first clues of Vostok; and Roland Psenner of the University of Innsbruck, one of the world's foremost authorities on Alpine lakes. Though Psenner has studied Europe's high lakes - from Spitsbergen to Spain's Sierra Nevada - he's never gotten close to Antarctica. Still, he was thrilled by the possibility that Vostok might contain living microbes from a bygone era.
"Since my focus is on microorganisms living in ice and icy water," Psenner said, "Lake Vostok is a target of high priority, and I am convinced that certain forms of life exist in the lake. But before even considering a study, we must do our homework and find a secure, clean sampling technique."
As Ellis-Evans, the organizer, scurried in and out of the conference room, torn between collating the science and arranging the coffee breaks, Robin Bell kicked things off with her now-polished Vostok 101 talk, which detailed the lake's geological history and its potential as a subject for study. Jean Robert Petit, a glaciologist with the Laboratory of Glaciology and Geophysics of the Environment in Grenoble and the French leader of the team that studied the climate core taken from below Vostok station, described the crystal structures found in the ice. "From a glaciological point of view," he said, "Vostok is a unique place to study a very long paleoclimatic record." Valery Lukin, a Vostok expert from the Arctic and Antarctic Research Institute in St. Petersburg, talked about the latest seismic work carried out from Russia's base, data showing that the northern end of the lake is a shallow, rocky swamp, while in the south, the waters are deep - and the sediments below them possibly deeper still.
It took just three hours to cover all the facts known about Vostok. After lunch - and over the next 24 hours - scientists ran through the seemingly interminable list of unanswered questions. For example, when a break-out group debating biological issues quizzed Ian Dalziel, associate director of the Institute for Geophysics at the University of Texas, about the nature of the hole that the lake waters are sitting in, he cheerfully told them that it could have been created by two continents colliding, a landmass tearing apart, a glacier, or even an asteroid - and that it could have been there for as long 35 million years.
Another point of contention is whether Vostok was a surface lake that froze during a past ice age or something that formed more recently from water trickling through the Antarctic ice cap. Apparently, there's no way to tell whether Vostok's bedrock cradle already had water sitting in it before ice first took hold of Antarctica 35 million years ago. "It's easy to speculate,"said Dalziel, "because there isn't any data. Until we drill it, we won't know for sure."
As luck would have it, the 1995 borehole for climate studies was drilled into an ice sheet whose bottom layer is made up of frozen water from Lake Vostok itself. Two teams at the Cambridge meeting had looked at samples of this refrozen water. One was headed by John Priscu of Montana State University, who has also researched the biology in Antarctica's surface lakes - which are frozen over but still receive enough light to perform photosynthesis. The other was led by David Karl of the University of Hawaii, an expert on marine microbiology who has observed life around deep ocean vents and in the nutrient-poor wastes of the North Pacific.
The two men - who have known each other for years - had no idea they'd both been working on Vostok problems until a few weeks before they presented their results at the Cambridge meeting. Priscu's and Karl's discoveries, published in separate papers in the December 10, 1999, issue ofScience, concluded that refrozen ice above the lake contained quite a lot of bacteria. Karl's team reported that some of these bacteria are still able to function despite their very slow metabolisms.
That there could be living bacteria in the ice above Lake Vostok isn't much of a surprise in itself. Vostok may seem extraordinarily isolated to humans, but bacteria experience it as just another place to turn up. And just turning up is what bacteria do best: They do it all over the planet. Admittedly, if the bacteria were migrating into the ice above Lake Vostok, they would have spent more time getting there than most anywhere else - sinking slowly through the ice cap, each new year's worth of snow forcing them that little bit deeper. It would be quite possible for bacteria to melt out of the ice over one part of Lake Vostok, drift through its otherwise lifeless waters for a bit, then get frozen back into the ice elsewhere, waiting for their next chance to turn up someplace interesting. If that were true, the bacteria in Lake Vostok would be no different from those trapped in the ice above it.
But it's also possible that the microbes Karl and Priscu retrieved from the ice are part of a viable ecosystem indigenous to the lake, consisting of organisms that have found ways to get on with life in cold, dark, nutrient-poor water for millions of years. If such an ecosystem exists, the likelihood is that it's sparse and staggeringly slow to replenish itself. "I would say a generation every hundred years might be feasible, if the lake's as low in nutrients as we think," says Jim Tiedje, a professor of microbiology at Michigan State University who studies the types of organisms that make their home in Antarctic ice.
The problem facing life in Vostok is that if microbes can't photosynthesize, they must rely on chemicals in the environment that have the potential to react with each other and release energy. Stripped to basics, this normally means an organism will need to take electrons from whatever it uses as food and give them to oxygen atoms. For this to be sustainable, the organism needs a reliable supply of oxygen to accept the electrons, which, happily enough, Earth's plants are able to ensure. Some bacteria use alternative electron acceptors - sulfate ions, nitrate ions, carbon dioxide - but these, in turn, are mostly made available by oxygen-dependent life elsewhere. If you look into the sediments under one of the microbial mats Ellis-Evans studies in Antarctica's surface lakes, you'll see this cascade of chemical dependency beautifully illustrated, with each layer using by-products from the one above: The ash from one biochemical fire becomes fuel for the next.
The microbial communities Karl studies around deep ocean vents - populations undreamed of a few decades ago - live in total darkness, but much of their energy use depends on electron acceptors that originate in the sunlit ecosystems far above. Without these imports from the world of photosynthesis, the ecosystems at the deep vents would have to get by on locally produced chemical imbalances that offer only a tiny fraction of the energy available to an ecosystem blessed with sunlight.
Some oxygen gets to Vostok through the ice - but most of it is likely trapped in little cages of water molecules called clathrates, and thus is probably unavailable to microbes. So if there's a microbial ecology in Vostok's depths, it's probably made up of the hungriest, slowest-growing microbes on the planet. To microbial ecologists like Tiedje, such a discovery would be fascinating in its own right. To earth scientists, it would offer new clues to the controversial "snowball-Earth" theory, which describes a series of catastrophes more than half a billion years ago that represent the most severe environmental crises ever.
It started when all life was microbial, the sun was dimmer than it is now, and the continents were clustered near the equator. Warm, wet soil absorbed more carbon dioxide than Earth's burden of life was producing. The greenhouse effect weakened, the world cooled, and ice spread over the oceans from the poles. Since more ice cover means more sunlight reflected back into space, things cooled down quickly. After the ice caps reached about 30 degrees latitude, the reflection effect became unstoppable, enveloping the entire planet in freezing temperatures and sending ice from both poles toward the equator. Every ocean, sea, lake, and river froze. With no sources of water vapor, clouds vanished from the sky. In the darkened oceans, photosynthesis shut down and the seas began to die. The snowball-Earth theory asserts that for roughly 10 to 50 million years the planet was reduced to a state close to death - probably very close to the state today of Vostok and, possibly, Europa.
While its seas were dying, though, Earth's nonbiological activities continued more or less as usual. Volcanoes pumped out fresh carbon dioxide, and since the newly frozen land was unable to absorb it, the gases built up in the atmosphere. Eventually, at the equator, the temperature rose back above freezing. The first cracks appeared in the ice. Water vapor, a powerful greenhouse gas, returned to the skies. That warmed things up further. More ice melted, more sunlight was absorbed, more water evaporated, and the temperature shot through the roof. Models suggest that it took only 100 years for the ice to recede back to the poles - a century during which the global mean temperature is thought to have increased by 122 degrees. Life leaped forth from its refuges in hot springs and lakes. With huge amounts of carbon dioxide and sunlight available, photosynthesis in the oceans ran riot, producing oxygen at an incredible rate. The wild warming after our last snowball Earth may have been the crucible from which the complex life-forms of the Cambrian explosion arose.
The snowball-Earth theory features prominently in the report that Ellis-Evans, Bell, and others are preparing to submit to SCAR on the need for further research into Vostok. The report covers all the areas outlined in Cambridge: the presence or absence of an exciting ecology, the geological setting, the effect of the water flowing into the lake from the ice sheet above, the circulation patterns of water that is very cold and under extremely high pressure, the record of climate and ice movements in the sediments, and the source and fate of the water itself.
"A system like Vostok's, isolated in the cold and dark, would give us insights to the likely environment on Earth when snowball conditions would have prevailed," says Ellis-Evans. "It would tell us about what survived and how it survived. Nowhere else on Earth is likely to do that."
Ricardo Roura is one of the handful of people who have spent a winter on Antarctica without any governmental assistance. In the early 1990s, Greenpeace set up a camp at the edge of the Ross Sea as part of its campaign for the ratification of the Madrid Protocol to the Antarctic Treaty, which imposed a 50-year moratorium on mineral exploitation. Roura was part of that camp, and his stay there taught him to love the barren land. As a coordinator for the Antarctic and Southern Oceans Coalition (ASOC), a group of 240 nongovernmental organizations from 50 countries with interests in the region, Roura spends much of his time trying to protect the Antarctic from environmentally disruptive projects. When it comes to Vostok, he doesn't think the scientists - particularly the NASA scientists - are taking those protections seriously. The exploration of Lake Vostok is just the sort of thing he wants to stop.
"Lake Vostok is to Antarctica what Antarctica is to the rest of the planet: remote, pristine, and unique," Roura told the Cambridge meeting. "You scientists have decided a priori that something must be 'done' with Lake Vostok as soon as technically possible, while the most appropriate option to protect the ultimate scientific and environmental value of Vostok would appear to be to postpone drilling the lake for the indefinite future." A particular bugbear for Roura is the idea that NASA wants to use Vostok as a test bed for technologies in development for Europa. He calls their interest selfish and shortsighted.
NASA puts a more positive spin on the situation. "One of the things we want to emphasize is that it really works both ways," says Joan Horvath, an MIT-trained rocket scientist and former manager of JPL's Europa-Vostok Initiative. "Because people are developing interesting technology that didn't exist before for space, we'll be able to go into the lake in a way that's clean and sterile and won't disturb it. You might not have been able to do that if you weren't trying to do both projects."
Nevertheless, activists like Roura and James Barnes, ASOC's general counsel and cofounder, continue to push for Vostok's protection. "In Vostok, we hope we can make the case for being cautious - not moving quickly to drill, considering all the options, and helping people understand what's at stake," says Barnes, who's also an attorney for Friends of the Earth International. Though Barnes never insists that exploring Vostok should be banned outright, ASOC is working through the International Union for the Conservation of Nature to sponsor a formal resolution that would halt drilling, going well beyond the protective intent of the Antarctic Treaty protocol. And if drilling proceeds anyway? "I seriously doubt that any Antarctic Treaty party would make such a move," contends Barnes. Though an ASOC resolution isn't binding, he says, the treaty's protocol is, and if a country violates it, environmental groups can file a lawsuit.
The scientists associated with Vostok don't share Roura's and Barnes' views. For them, Vostok isn't just an abscess in the ice but a hole in our knowledge of the world - a peculiarly well-defined, romantically isolated, technologically dramatic hole. For good or ill, part of being a scientist is to find such holes irresistible. "Subglacial lakes are a brand-new environment," notes Ellis-Evans, "and, like anywhere humans come across, we are curious about it - we want to understand it. Whatever else, the place is a mystery. Scientists, being human, will always want to investigate a mystery. You cannot simply ignore it."
It's not that the scientists don't have doubts about what they're doing: The urge to protect and the urge to study still take turns leading their dance into the depths. If the lake is contaminated, measurements and samples will be compromised. But there's a deeper unease, too. "We have detected, explored, and spoiled almost all sites of the world, and we are going to do so with extraterrestrial systems," said Psenner in his Cambridge presentation. "Why not leave Lake Vostok in the mythical darkness?" But the nature of their profession is to overcome those doubts. As Psenner said at the meeting's end, "Vostok is possibly the only pristine lake we have left on Earth, and we should be extremely careful - but I'm too tempted by it not to go."
Put enough Vostok researchers in a room, and the lake will seem as hemmed in by different lines of questioning as it is by ice. But when it comes to Europa, there are really only two questions that count: Is there an ocean? And is anything swimming in it? In the pictures sent fromVoyager probes in the 1970s and byGalileo during the past five years, the Jovian moon looks like an antique billiard ball - a smooth sphere of spreading cracks and stubborn stains. Europa's icy surface is indeed ancient by most measures, but by planetary standards it's freshly minted. A relative absence of impact craters suggests that the outer crust is only 100 million years old, in parts much less. Since Europa is a small world, half the diameter of Earth, this is quite surprising: The heat should have drained out of Europa's tiny core ages ago. But Jupiter's massive gravity alternately stretches and compresses Europa, and this kneading generates heat through friction. In fact, it may create enough heat to liquefy an entire ocean's worth of water under a layer of ice only a few miles thick. That makes it "a fascinating place - and a prime place for space missions," says Frank Carsey, a team leader of the Polar Oceanography Group at JPL, which does ice research in Antarctica.
The idea of a habitable ocean locked beneath the permanent ice cap on Europa excites planetary scientists because on Earth, at least, all life requires liquid water. And beyond Earth, there's little direct evidence of any liquid water. Venus has baked itself into aridity. Mars was apparently wet once, but aside from its ice-capped poles, the Red Planet makes the Gobi desert look like a swamp. Comets and some asteroids contain ice in abundance - but if ice were what life needed, Antarctica would be green, not white. It's liquid water that counts, and Europa, with an ocean possibly greater in volume than all the oceans on Earth combined, offers a lot of it.
Every observation made withGalileo's instruments seems to argue for a Europan ocean. A follow-up probe, the still-unnamed Europa Orbiter, will be launched in 2003 to put the matter to rest. The craft will circle Europa from 124 miles above for nearly a month, measuring the tidal rises and falls of its surface with a laser altimeter. If the ice sits on rock, the tides will be small - solid ice would deform only slightly under Jupiter's insistent gravitational pull. But if there's water below the ice, the tidal bulge should stretch the moon's surface dramatically.
At many scientific centers - including the National Academy of Sciences, which keeps watch over NASA's science priorities - evidence of a Europan ocean would place it alongside Mars as the focus of the search for life elsewhere in the solar system. If the proposed Europa Orbiter confirms an ocean's existence - which most believe is 90 percent probable - a series of missions to Europa is likely to follow. "I'd bet there's life on Europa," says Richard Greenberg of the University of Arizona's Lunar and Planetary Laboratory in Tucson and one of the scientists analyzing imagery from Galileo. "I wouldn't bet there's life on Mars."
Finding life, either in Vostok or on Europa, requires drilling through an icy crust, which means resolving a multitude of engineering obstacles. While exploring a subsurface Antarctic lake is tricky, it doesn't compare with the logistics of controlling a probe in the solar system's farthest reaches. Horvath addressed some of those obstacles in 1996, when she asked her undergraduate students at Caltech and the UK's Leicester University to think about ways to get through Europa's crust to the putative ocean beneath. They soon realized that experts on earthly ice caps would have something useful to say about the matter. As it happens, JPL employs several climatologists, including Carsey, who had an interest in Antarctica. After their first meeting, he and Horvath resolved that Europa and Vostok were pieces of the same puzzle. "He says I thought of it; I say he thought of it," Horvath says with a laugh. The two of them attracted a clique of fellow Vostok enthusiasts who met regularly to discuss the kinds of hardware and strategies required to study life in dark waters under deep ice.
"The key technologies," Carsey explains, "are decontamination, then robotics, then instrumentation, then communications." In each area, the difficulties of drilling down to Vostok should illuminate the challenges of burrowing into Europa. There are, of course, major differences between the two projects. A probe going into Vostok can expect some hands-on help; a Europan probe will have to make its own decisions halfway across the solar system.
Carsey's cryobot offers a preview of what the probe might look like. He says it will be able to puncture a hole through the ice sheet with a hot-water drill, bathe itself in sterilizing chemicals, then cruise Vostok's deepest reaches. "It's probably not that hard to make a cryobot," says Carsey, "but to make one that's reliable and optimized - that's a little involved." If he can secure funding from the National Science Foundation, the first $100,000 prototype should be ready by summer. And in less than three years, he says, one of these icebots should be finished and ready for field testing.
During these trial runs, humans will be on hand to drill the cryobot's access hole and monitor its descent. The fuel needed to create boreholes in the ice will be flown in on C-130s by the New York Air National Guard, which supplies logistics support throughout the Antarctic. Such a cryobot would be employed for a Europa mission as well, which Carsey is considering as he puts together a blueprint for its design. But on Europa there would be no lifeline for handlers trying to send instantaneous commands to the bot far below: Signals sent to Europa will take 35 to 50 minutes to reach the probe in a place that makes Vostok station look like Mauritius. Europa's surface gets no warmer than minus 250 degrees, the sunlight is 27 times dimmer than it is on Earth, there's no atmosphere to speak of, and the place is continuously bombarded by a vicious hail of particles from Jupiter's radiation belts.
Just getting to Europa is hard enough. The orbiter due to launch in 2003 will take almost three years to reach the moon, and radiation damage to its solar panels will make it reliable for only one month of work after it arrives. An energy-intensive project like drilling a hole through the ice will almost certainly require nuclear power - technology NASA has employed before, but which encounters increasing opposition. "Some environmentalists complain that the radiothermal generators are dangerous to launch, and are pollutive once they get to their target," says Carsey. "Both are arguably true. But the RTGs are designed to survive a launch calamity without breaking up - and, in a case like Europa's, the surface of the planet is far more radioactive than the RTG itself."
Lake Vostok's mystique is drawing people like Arthur Lonne Lane, a colleague of Horvath's and Carsey's at JPL who is taking what he's learned building spacecraft instruments and applying it to developing "technologies to solve some of the problems we'll face once we begin the scientific explorations of Lake Vostok and Europa." A device entering Vostok - and, someday, Europa's oceans - would have to be extremely compact, he says, small enough to be contained inside Carsey's cryobot. "The deep-water cameras they put on Alvin and other submersibles take beautiful pictures, but their housings are big and long," he says, going on to describe something about the size of a filing cabinet. "They have a huge glass dome at the front and these enormous outside arc lights."
Lane's instruments, by contrast, are economical: long, thin tubes of titanium built to be stuck into volcanic vents on the ocean floor. His latest camera - which has worked at depths of 1.2 miles - uses optical fibers to shine light from internal lasers out into the world, with a camera and spectrograph peering through a small, sturdy window at whatever they illuminate. "We developed a camera system that could operate at 400 degrees Celsius (752 degrees Fahrenheit), appropriate for hot vents and future deep-atmosphere probes of Jupiter, Venus, and Saturn," says Lane. "For Vostok and Europa, hot temperatures aren't anticipated, so the existing design wouldn't change a bit." In November, Lane will send a newer version of his imaging system nearly a half-mile into an Antarctic ice floe to study its base - a shakedown for future missions to Vostok and Europa.
Lane's camera would get to the bottom of an ice sheet with the help of Hermann Engelhardt, a glaciologist at Caltech. Engelhardt studies the conditions that lubricate ice sheets and glaciers as they move across terrain. This means he needs ways of looking beneath the ice, and his tool of choice is the hot-water drill - a vertically mounted, high-pressure fire hose. Hot water cuts through the ice ahead, and cooler water is pumped out of the hole from behind the drill head, then reheated and pumped back through the nozzle. In 1998, Engelhardt used this technology to drill 43 holes, each through an ice sheet in a couple of months, leaving instruments underneath that he could then contact via satellite from his laboratory in Pasadena. Next year he'll lower one of Lane's probes into such a hole to see what's going on in far greater detail.
So when can we expect the first mission to get under way? After Carsey's cryobot - which incorporates Lane's camera and Engelhardt's drill - has been tested, after governments have agreed to pay, after environmental-impact assessments have satisfied the watchdogs at SCAR, and after further surveying has provided precise data about the lake's shape and the distribution of its sediments. When will that be, exactly? "I have a different answer every time somebody asks me," says Carsey. "What I really think is that we're probably about five years away."
But whether it's five years or twice that long, he sees the mission's progress like this: First, a hot-water drilling system creates a borehole down to within 500 yards of the lake's surface. "The approach is nice and fast," says Carsey. "It would maybe take a week to get to that depth." A long, thin cryobot, meticulously cleaned and packaged in a sterile wrapping, is lowered nose-first into the hole. "The working versions would be made of stainless steel or titanium," he says, "cylindrical in shape, probably 10 to 15 centimeters in diameter - small is better - and 1 to 2 meters long."
Once the cryobot is in position, the water above it is allowed to freeze, and a sterilizing solution is released. Electric current starts to flow down the 2.5 miles of cable - now sealed in ice - that link the cryobot to its controller. The probe's nose starts to heat up, a little of the surrounding ice starts to melt - slowly at first - and the cryobot starts to sink under its own weight. Pumps in its flanks suck up some of the melted water, which is reheated and pumped back out through the nose. This self-contained hot-water drill burrows downward, paying out fresh cable. As the probe sinks, the hole behind it freezes up. It comes to the lake's surface, pauses, and enters. Only the cryobot goes in; only information comes out.
The cryobot hangs still for a while just beneath the ice, its lasers the first source of light to illuminate the lake in millions of years, shining a few tens of yards into the darkness. The camera surveys the ice surface, searching for any clumps of matter and reading their spectral signatures. Digital images start to flow up through the ice, out to the satellites above and to waiting scientists all around the world. Next, the cryobot begins gathering water samples, running tests to reveal any microbial activity. "We want images and chemical and biological data," says Carsey, "with data-handling systems on the bot and on the controller."
Slowly, the probe pays out more of its lifeline. Its sensors alert for any slow currents - for any subtle distinctions between layers of water - it sinks below the lake's top layer of ice. The drilling pumps come back to life, nudging the probe gently from side to side. A pendulum in the dark, it swings back and forth, deeper and deeper. Eventually, it all but grazes the lake-bed sediments, scanning for clues to an unseen ecosystem. Finally, its oscillation damped, camera rolling, it hovers motionless, while the sensors embedded in its flanks scoop up sediment samples, sniffing out any potential for the production of energy - a sign of the fires of life.
And after that? More sophisticated instrumentation, the return of sediment samples to the surface (a far more difficult proposition that Carsey refuses to think about on the grounds that he'll be retired by then), perhaps even free-swimming robots that could seek out signs of hot springs.
And what about Europa? Armed with Antarctic experience and the results from the Europa Orbiter, Carsey imagines the first generation of extraterrestrial cryobots could be in full development later this decade. By the '10s and '20s, exploration of the satellite's ice and water should begin in earnest, an effort that will dwarf the Vostok research both in cost and potential reward: evidence of life elsewhere in the solar system.
Caltech's Joe Kirschvink, the earth scientist who came up with the notion of the snowball Earth, thinks finding complex organisms in the Europan depths is a long shot. With no surface life to supply electron acceptors, the ocean wouldn't offer chemical imbalances strong enough to keep life going. Earth's snowball episodes were planetary near-death experiences. Europa's far-longer freeze would be terminal. Other scientists are more optimistic, seeing alternative chemical states for the ocean that might yield viable environments. The radiation that makes the moon's surface so inhospitable might turn out to be a blessing in that the chemical radicals it creates in the ice could somehow make their way to the ocean and provide another source of energy.
The University of Arizona's Richard Greenberg argues that people doubtful about life on Europa are ignoring evidence that the ice is very thin in some places, which means there could be water close enough to the surface for photosynthesis to occur. The lake's organisms would spend most of their time frozen and inert, springing into action only when the tides created new cracks to feed them water - or when a burrowing cryobot passed by.
Whether Europa harbors life or not, it will merit many decades of exploration. Over that sort of time span, Vostok's comparatively meager supply of knowledge will be drained, and knowledge is the only thing Vostok has to offer: It's hardly a place where anyone might try to live. Mars could one day be colonized; eager scientists might push for a base on Europa if the natives there were interesting enough. In some distant century, we could even establish outposts on planets in other solar systems. But there's no reason for humans to venture in person to cold, delicate, joyless Vostok, so there's no reason - after scientists lose interest - that Vostok shouldn't be returned to its previous isolation, left just as we found it, emptied of knowledge yet still filled with that gin-clear water.
Restored to its mythical darkness, Vostok's isolated ecosystem could last a very long time - longer than a mountain range, perhaps longer than an ocean basin. The East Antarctic ice sheet would most likely remain stable, even under severe global warming. In fact, there's no compelling reason to think it will disappear, until the insulating ring of ocean currents that cut it off from the warmer world is interrupted by some new arrangement of the continents.
In time - when ice has covered Vostok for two, three, or four times longer than it has so far - tectonic forces will pull the frozen continent away from its wallflower existence at the pole, nudging it closer to the growing low-latitude supercontinent of Asia-Australia. The ocean currents will shift, the warmer weather of the north will start nibbling at the ice. As the heavy ice sheets begin to melt and slip away, the continent will rise up, its unburdened rocks suddenly buoyant. Hills once hidden beneath ice will rise to become mountains. Life will reappear: soil bacteria, lichens, insects, and flowers seeded by the wind. Birds will return - first to the sky, then to the softening soil. In the end, the sun's faint glow will reach down through the last remaining lens of ice. After the longest night, a soft, diffuse dawn will come to Vostok. The thinned ice will crack, and the waters will suck new breath from the sky. The 100-million-year voyage through the darkness will end. And if it was ever there - if it managed to survive, if we did our part to protect its uniqueness - an age-old ecosystem will become a new scrap of food for the creatures of a strange, changed world.
