Geotimes
Technology
3-2-1 Meltdown
Christina Reed

At the end of October last year, weeks behind schedule due to logistics after September 11, task manager Lloyd French and six of his teammates on the Cryobot project found themselves north of the Barents Sea on Spitsbergen Island in Svalbard, Norway.

This would be the first true field test of the Cryobot, the only vessel currently being primed to take scientific equipment on a journey through ice anywhere in the solar system without fear of contaminating the environment.

The team was gratefully in the hands of the Norwegian Polar Institute and Norwegian Space Center. The Norwegians scooped up the California-based scientists and their gear into a helicopter and flew them to the Longyearbreen Glacier, a five-hour hike for adventurer-tourists visiting the town of Longyearbyen.

Researchers from NASA's Jet Propulsion Laboratory and the California Institute of Technology suspended the Cryobot from a tripod during its first field test in the Arctic. From left are Robert Ivlev, Daniel Helmick, Wayne Zimmerman and Lloyd French. Courtesy of NASA/JPL.

“We had a 10-minute ride out of town with the flop, flop, flop, sounding blades of the Bell 212,” Lloyd says. “The skids landed on the ice and everyone jumped out to set up a depot area. The snow was heavy and blowing roughly 10 to 20 knots — just crazy. We were battling to get the gear off and set up in whiteout conditions with a wind chill about negative 30 degrees Celsius.”

In 1999, NASA approved funding the Cryobot project $1.3 million over three years. The hope was to build a vehicle that would allow scientists to search for life in ice not only on distant bodies in the solar system but also in the 4 kilometers of glacial ice covering the pristine Lake Vostok in Antarctica. But it soon became clear that the project would have many obstacles to cross. Within six months, due to budgetary pressures, the funding was cut for the second year, and the third year was canceled all together, Lloyd says. “I had $600,000 to keep 10 people alive. The team put a lot of heart into that project.”

The team hopes that the Cryobot, a torpedo shaped vessel geared with a hot nose for melting its way downward under the force of gravity, may find its first official tour-of-duty on Mars. Currently the Cryobot is among 10 projects bidding for the 2007 mission to the Red Planet. In June, the Cryobot engineers at the Jet Propulsion Laboratory (JPL) in Pasadena, Calif., will pitch their scout proposal to NASA and cross their fingers for more funding.

In September 2000, after a year of performing melting experiments in the lab with a prototype Cryobot, the engineers constructed a 20-foot tower outside their lab to hold large blocks of ice. The team witnessed the first plunge of the Cryobot through 5 meters of clear ice normally intended for sculptures. “This deployment validated many of the Cryobot’s systems and gave us our longest descent depth,” says systems, integration and testing engineer Gindi French. She became involved with the idea of the Cryobot in 1997 when Frank Carsey and Arthur Lane, also at JPL, first proposed the concept.

Carsey had in mind updating the old thermal probes of the 1960s to explore for life on Jupiter’s moon Europa. Intrigued, Gindi worked with another student to design and test a mini-Cryobot, until funding came through for the real thing.

Lloyd French first became involved with the Cryobot in October 1999, when NASA hired him as task manager for the team. Previously he built vessels capable of withstanding the high pressures of the deep sea. Like everyone else at JPL, Lloyd and Gindi have multiple projects in various states of design or testing, but the Cryobot at least is one project they work on together.

The first-year model of the Cryobot performed well through the trial ice. “However, we were not in a challenging field location, such as Svalbard,” Gindi says.

During the hoped-for mission to Mars, a lander would set down on the north pole and quickly deploy the Cryobot to melt its way about 200 meters into the ice. At the Longyearbreen Glacier it took two days to set up the site, put up a perimeter fence as a polar bear deterrent, unload the Cryobot and make sure all systems were go. Instead of a lander the scientists used a tripod.

On the glacier, a tether deployed from the surface linked the robot to the control station and supplied the probe with about 900 watts of power, the equivalent of about 10 light bulbs. “We have limited ourselves to using a 1 kilowatt power source to make the Cryobot more realistic for use in space flight,” Gindi says.

They slept in tents taking turns on watch for bears and over the Cryobot. “We had no problem with polar bears,” Lloyd says. “Braving the cold and the fact that we had no light — that was hard.” The October sun north of the Arctic circle is on a fast track to a long winter night. The trip lasted about 12 days. “We were losing about 30 minutes of light every day. When we started it was more like twilight, when we left it was dark.”

Their biggest concern was ice quakes and crevasses. “I could just imagine a crack going through the area when we were on active melting,” Lloyd says with a shudder. Passive systems of melting, such as on previous thermal probes, depend on heaters in direct contact with the ice. Active systems like hot-water drills generally use more power, but can zip through dust layers that have the potential to stop a passive system in its tracks. The Cryobot has both types of melting systems, uses little power and, because it can adjust where the heating is directed, has some means for avoiding obstacles.

The passive melting utilizes heaters on the nose of the Cryobot to warm ice above its melting point. The whirlpool of water travels about 20 centimeters from the nose to where it is sucked into a filtration system. The Cryobot then turns into an overzealous coffee pot: An emersion heater warms the filtered water to about 10 to 15 degrees Celsius and jets it out the Cryobot’s nose as a means of actively heating the ice and of washing away any salt or dust buildup.

Gravity keeps the probe and its Jacuzzi system traveling straight down, but only a small gravity field is needed. About a meter long and 12 centimeters wide, the Cryobot leaves a small rabbit hole in the ice that eventually refreezes as the probe travels deeper and the increasing pressure closes the ice in behind it. By the end of the field test in Norway the hole was about the size of a dime, just big enough for the tether. For deeper missions, or where biological contamination concerns demand that the hole refreeze solid, then the probe can carry its own spool of cable.

An artist's illustration of a lander deploying the Cryobot on an icy planet (NASA/JPL)

After various active and passive testing the Cryobot reached a record of 23 meters deep. The researchers believe they can engineer the Cryobot to travel further than 1 kilometer, but the weather turned ugly enough to call off the field test. With the aid of a mini-hot-water-jet drill, the team remelted the hole, reeled out the Cryobot, packed up the tents and headed back to the town of Longyearbyen. “The Norwegian Institute and Space Center were very helpful in achieving this milestone. We couldn’t have done it with out them,” Lloyd says.

While the Cryobot can melt as much as 1 meter an hour, faster is not necessarily better. “Slow and steady could win the race on this one,” Lloyd says.

“On average our Cryobot has descended at about 0.75 meters per hour,” Gindi says. At that rate sensitive scientific equipment the Cryobot will carry, such as a camera, can obtain accurate readings of the surrounding ice. But the colder the ice the more power is required. The Gulf Stream feeds into the Barents Sea and warms the glacial ice on Longyearbreen to about -9 or -10 degrees Celsius.

“In Antarctica the surface ice is negative 55 degrees Celsius,” says Frank Carsey, Team Leader in Polar Oceanography at JPL. “In Greenland negative 35; at Mars negative 110; at Europa negative 180 degrees Celsius.” At those temperatures, power of 2 to 3 kilowatts might be needed. The engineers are also considering using an interior power source without a tether to the surface.

When Carsey saw Galileo’s first images of Jupiter’s moon Europa in 1996, he reacted with the joy of discovery. “That is great ice,” Carsey remembers thinking. “In fact, I thought: I’ve seen ice like that on Earth,” he says. The Galileo data converted the polar oceanographer into a planetary scientist. “I used to think it was an oddball occupation I couldn’t imagine anyone getting serious about.”

The broken-glass appearance of Europa’s Conamara terrain with its crisscrossed ice floes reminded Carsey of sea ice he had seen on excursions around Antarctica and off Canada’s northeastern coast in the Labrador Sea. After colleagues at JPL asked Carsey what it would take to get through the ice, it wasn’t long before they were pitching the idea of a Cryobot to NASA. “The best way of getting into a deep chunk of ice on a distant planet is with a thermal probe,” Carsey says.

Soon after NASA approved funding the Cryobot, the vulnerability of exploring Lake Vostok became crystal clear. In 1999, David Karl of the University of Hawaii and John Priscu of Montana State University independently identified biological life forms from the bottom of the Russian ice core taken within 400 feet of Lake Vostok that appeared to be from the refrozen surface of the lake under the glacier (Geotimes February, 2000). But kerosene, freon and other drilling fluid that kept the deep pressures from closing the core made it unsafe to drill any further. The scientists all agree any method for reaching the lake must be free of contaminants and organisms.

While the Cryobot with each new design phase becomes a better example of the technology capable of reaching the lake safely, the Scientific Committee on Antarctic Research (SCAR), which Carsey consults, is undecided over how clean is clean. Previous thermal probes of the 1960s lacked such engineering insights as a tether that would unwind from inside the probe, allowing the tunneled ice to refreeze without breaking the connection between the probe and the surface. With the ice freezing closed behind the Cryobot, the probe could cleanse itself with a hydrogen peroxide bath, for example, and continue picking up whatever exists in the surrounding glacial environment. Would it need to cleanse itself again before breaking through to the lake surface? How effective is the hydrogen peroxide bath? How would it be administered and how much would be needed?

“All unknowns,” Carsey admits. “Peroxide is effective against almost all microbes although there are a few anaerobes that are able to metabolize the stuff at low concentrations, so it cannot be called utterly effective.” Although they don’t expect anaerobes in the ice they might consider several other options for sterilization.

“The methods for contamination control varies like the rainbow,” Lloyd says.

“Ozone for example, which can also be made in-situ,” Carsey adds. “There are also commercial sterilizers, which have benign byproducts, but these have to be brought along [during a mission] and are less convenient in some situations.”
But whatever the requirements the engineers are not dropping their Cryobot into Lake Vostok anytime soon. For one, “It certainly wouldn’t float,” Carsey jokes. Indeed, the Cryobot would release a hydrobot for that mission. But then, that is another project and they have Mars to think about right now.


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