Putting untethered vehicles under the ice cap is one thing. Getting them back is another. In the summer of 2007, an international team led by scientists at Woods Hole Oceanographic Institution sailed to the Arctic Ocean aboard the Swedish icebreaker Oden. Their missions: to test new robotic vehicles designed for use in ice-covered oceans and to search for volcanic activity and new deep-sea life forms on the previously unexplored Gakkel Ridge.
This story begins on a moon of Jupiter and in a bathtub.
The bathtub was on Earth, and in it was Cassidy Reves-Sohn, just a few months old and being scrubbed by her dad, Rob. As is often the case in these situations, the tub was full of soap bubbles and bobbing toys, including a Sesame Street submarine, captained by none other than Elmo.
If you've ever been a parent giving your kid a bath, or a kid being given one, you know that bath times are also full of fantasy. No one knows what Cassidy was fantasizing about. But to her father - an earth scientist who studies the seafloor - the white layer of bubbles suddenly reminded him of the sea ice that covered the Arctic Ocean - and blocked scientists' ability to get to the bottom of it. Wouldn't it be neat, Reves-Sohn thought, if we had vehicles that could safely explore below the ice and resurface again, as easily as Elmo's sub?
That was ten years ago, about the same time that the space vehicle Galileo, orbiting a moon of Jupiter called Europa, found that the moon's surface was an ice-covered ocean. Space scientists also calculated that the massive gravitational forces exerted by Jupiter on its tiny moon likely caused volcanic activity on Europa.
It was only 20 years before that, in 1977, that scientists had discovered, much to their astonishment, that those same two ingredients - volcanism beneath an ocean - created conditions for life to thrive on Earth.
Along the Earth's volcanic mid-ocean ridges, seawater seeped through cracks in the seafloor and were heated by volcanic rocks below. The heated seawater chemically reacted with rocks and rose like geysers on the seafloor. These so-called hydrothermal vents discharged chemical-rich fluids that sustained lush communities of life in the absence of sunlight.
If such life were possible on Earth, why not on Europa? Jupiter's moon became a prime future target for space scientists to search for extraterrestrial life in our solar system.
Meanwhile, to earth scientists like Rob Reves-Sohn, the bottom of the Arctic seemed almost as remote, inaccessible, and unexplored as Europa. In the mid-1990s, around the same time as Cassidy's bath, the U.S. Navy for the first time offered nuclear submarines to the scientific community for unclassified Arctic research. A few submarine missions used sonar to make maps of the Gakkel Ridge beneath the eastern Arctic Ocean.
It wasn't until 2001 that scientists secured an icebreaker for the first research cruise dedicated to sampling the Gakkel Ridge. The ridge was not supposed to be very volcanic, so the scientists were surprised when they found strong evidence of plumes from hydrothermal vents.
Now the threads of these stories come together. Rob Reves-Sohn, working with engineers at WHOI, followed his dream to develop robotic underwater vehicles that could explore beneath the Arctic Ocean. The National Aeronautics and Space Administration (NASA) was interested in developing robots that someday could search for life beneath ice-covered oceans on planetary bodies such as Europa. And earth scientists were eager to return to the Gakkel Ridge with vehicles that could find and explore hydrothermal vents, and possibly undiscovered life forms around them.
NASA funded development of experimental under-ice vehicles, and the Arctic offered a real-life, Europa-like environment to test them. The National Science Foundation funded an expedition, with Reves-Sohn as chief scientist, to try to use these experimental vehicles to explore the Gakkel Ridge.
And that, in a nutshell, is how we all got to Svalbard, an island above the Arctic Circle, from which we set sail yesterday aboard the Swedish icebreaker Oden, headed into the ice pack toward the Gakkel Ridge.
— Lonny Lippsett
The hunt for red hot hydrothermal vents
Hot, mineral-rich fluids gush from hydrothermal vents on the seafloor. To search for vents and the animals that live around them, scientists floating atop the ice-choked Arctic Ocean first look for plumes of fluids that trail out from the vents and drift in the depths.
"Plumes are a little bit like smokestacks from factories," said Hanu Singh, a scientist in the WHOI Applied Ocean Physics and Engineering Department who led a five-year effort to build new deep-sea vehicles for under-ice operations. "The smokestack has a diameter of only a few meters. But as it spews out smoke, the smoke usually rises up in a straight line vertically, and then it starts spreading out horizontally over large areas. Hydrothermal vent plumes work similarly and can lead us back to their source."
It isn't easy. "Picture this," the July 6 dispatch on Dive and Discover read. "There is a group of people you want to find. They are huddled around a small campfire. The campfire is in an impenetrable desert so you can't walk in. Your only hope is to fly a helicopter above the desert to see if you can spot the smoke from the campfire. But thick fog hovers a few miles above the desert. ...So you put a thermometer and a smoke detector on a long wire that you lower down through the fog in a place where you think there might be smoke, and then you hope your tiny instruments run into it." See Slideshow No. 1.
At the mercy of the ice
Sending an untethered robot into the depths is relatively simple. Bringing it back from beneath the ice was daunting.
In most oceans, deep-sea vehicles rise to the surface after completing their missions and are recovered by ships. The Arctic Ocean ice pack, up to 4 meters (13 feet) thick, proved a formidable, relentless, and unpredictable obstacle. Ensuring that the vehicles did not get lost or trapped under the ice, or damaged by it, was "a difficult technological task," said Rob Reves-Sohn, the expedition's chief scientist.
"Nobody's ever done that before, so we didn't have much experience," he said. "You can plan and plan and plan, but you don't know what will happen until you actually do it. We knew the vehicles had a very real chance of failing, and even being lost under the ice."
WHOI engineer Hanu Singh said: "We have a saying in the underwater world: ‘The number of vehicle deployments should equal the number of recoveries.' " See Slideshow No. 2.
In the end, the researchers did not find hydrothermal vents, but they did discover curious mats of yellowy-orange "fluff"-composed of microbes and/or material made by microbes, perhaps fed by a weak flow of chemical-rich fluids seeping out of the seafloor. See Slideshow No. 3.