Space pioneer: The ENDURANCE robot will dive to the bottom of an Antarctic lake this month. Such tests fuel research into future space-based robots that could one day explore oceans on other planets.
Credit: John Rummel, NASA
Looking something like a large yellow seed pod, a submersible robot is preparing to go where nobody has ever gone before.
If all works according to plan, the probe will shortly be lowered through a hole in the ice covering a lake in Antarctica's McMurdo Dry Valleys. After a thorough search around, it should return to the waiting researchers brimming with useful data.
The probe, called ENDURANCE (Environmentally Non-Disturbing Under-ice Robotic Antarctic Explorer) is the NASA-funded brainchild of William Stone, president of Stone Aerospace Corporation in Austin, Texas.
Its purpose is to use sonar to map, navigate, and explore unknown, dark environments, beginning in Antarctica, but possibly someday extending into space. NASA's involvement stems from a program that helps develop methods for exploring remote environments.
Deserts of ice
The current target, Lake Bonney, is six kilometers long, 900 m wide, and perpetually covered with several metres of ice. It's been studied for years, but ENDURANCE, which could begin its explorations this month, will open an entirely new frontier.
The lake is part of the Dry Valleys, which lie more than 3,000 km south of New Zealand. But the term "dry" is a misnomer. "They're 'dry' because there's basically no glacier," said Peter Doran, an Earth scientist at the University of Illinois in Chicago, USA.
That's because mountains block the largest ice sheets; though there are still several smaller glaciers spilling off the 3,000-metre peaks.
ENDURANCE isn't like the Mars Rovers or other remote-operated probes. Once deployed, it's on its own to systematically explore, take water samples, and find its way back. "It will have to think on its own," said Doran, outlining the plan at a scientific meeting.
Back-up plan
There is, of course, a backup in case the robot submarine (named for British Antarctic explorer Ernest Shackleton's famous ship) gets lost. If necessary, the scientists can locate it magnetically, drill a new hole, and send down a team of divers to retrieve it.
Not only is it too valuable (US$ 2.3 million) to lose, but it is also supposed to be environmentally friendly. "We were required to [have such a plan], rather than leaving that hunk of metal down in the lake for all eternity," Doran said.
Not that anyone really expects the probe to get lost.
In May, 2007, working under the name Clementine, it reached the base of El Zacaton, a 319-metre sinkhole in Mexico's Yucatan Peninsula – too deep for any human cave diver to have found the bottom and survived. In addition to mapping the cave, Clementine took water measurements and scraped previously unknown bacteria from the walls, all while out of contact with its operators.
Then, in February 2008, it was tested under-ice in a frozen lake near Madison, Wisconsin, in the USA. It found its way back, and demonstrated that its electronics functioned perfectly well in cold water.
At Lake Bonney, ENDURANCE will not only map the lake and explore its biology, but also take a close look at the base of a feature called Blood Falls, where reddish, iron-containing salts spill out of the face of a glacier at the lake's upper end.
Probing a mystery
But while there's much to learn from Lake Bonney, all eyes are fixed on an even larger goal. Someday, Stone's crew hopes, ENDURANCE's robotic descendents will unlock the secrets of Lake Vostok, one of the world's largest, deepest, and most mysterious lakes.
Lake Vostok is also in Antarctica, but it's beneath 3.5 km of ice. It first came to light in the 1970s, when researchers noticed odd radar echoes bouncing off the bottom.
"Ice is transparent to radar at frequencies of megahertz," says Donald Blankenship, a University of Texas researcher who hopes someday to use radar to peer through the crust of Jupiter's icy moon Europa, also believed to have water beneath its surface.
But the radar of the '70s was primitive, and nobody was quite sure what was being seen. Then, in 1996, airborne and space-borne instruments were able to take a more detailed look.
What they found was an enormous body of water – approximately the size of America's Lake Ontario and hundreds of metres deep. Since then, about 140 more sub-glacial lakes have been found, but Vostok remains the largest.
Extreme life
Particularly interesting is the question of whether the lake might contain a functioning ecosystem.
By the 1990s, scientists had been finding life in the oddest of places: inside rocks, deep beneath the sea near hydrothermal vents – places seemingly cut off from the normal processes of the outside world.
But it wasn't clear how to peek into the lake without contaminating it, either with drilling fluids or microbes carried down from the surface.
Early drilling efforts were discontinued as too risky and, due to ongoing controversy, are still postponed. According to a recent report in Nature, the Russians will wait until at least 2009 to 2010 before attempting to reach into the lake.
When they do, the first scientists will be thrilled just to take samples. But soon enough, they'll want to explore. And that's where ENDURANCE's experience at Lake Bonney comes into play.
Lake Bonney is shallow (40-metre-deep) and a relatively easy place from which to retrieve a wayward probe.
In Lake Vostok, retrieval would be well-nigh impossible. ENDURANCE itself is too big, and not strong enough, to be sent though a borehole into Lake Vostok. But it does provide a way of testing the systems that would guide and power a smaller, hardier probe of the future.
Space: the final target
But even Vostok isn't the ultimate target. It's simply another good springboard for an even more ambitious project: Europa. Scientists are increasingly convinced that Europa has an ocean and that it might be only a few kilometers beneath the surface.
"We think [it's] close enough to the surface to be accessible," said William B. McKinnon, a professor of Earth and planetary science at Washington University, in St. Louis, Missouri.
And, he noted, astrobiologists think that it might possibly contain (or once have contained) life. "I can't think of any more important question."
Richard A. Lovett is a writer based in the U.S. city of Portland, Oregon. He is a regular contributor to Cosmos.
