Published online 30 April 2011 | Nature | doi:10.1038/news.2011.261

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Novel design could help probe explore frozen environs on Earth and beyond.

The IceMole team loads their hybrid probe into its launch rack. FH Aachen / www.lichtographie.de

Getting a probe to travel five metres might not seem like a much of a reason to celebrate. But after Bernd Dachwald and his team watched their IceMole robot autonomously drill through a small section of Morteratsch Glacier in Switzerland during the summer of 2010, they held a small party.

"This was a major milestone," says Dachwald, an aerospace engineer at Fachhochschule Aachen University of Applied Sciences in Aachen, Germany. On 27 April, Dachwald presented results from IceMole's first field test at the 2011 Antarctic Science Symposium in Madison, Wisconsin. "We have proof that IceMole works not only in the lab but also in a real environment," he says.

After two years of work, the researchers believe they have developed a new type of ice-melting probe, which may one day penetrate sub-surface lakes in the Antarctic, dig through the ice caps of Mars or churn through the frozen crust of Europa.

Probes with heated tips have been used since the 1960s to bore through ice, but engineers found that dirt and sediment would often build up at the robot's head, impeding the transfer of heat. And most of these designs had the capacity to move in only one direction: down.

IceMole includes a six-centimetre screw at its heated head, which allows it to keep in firm contact with the ice surface it is trying to melt. The screw's grip means the probe can pull itself horizontally through ice layers and even upward, against gravity. The configuration permits the robot to easily penetrate dirt and should even work in places where the ice is in a near vaccuum, such as a comet's nucleus, says Dachwald.

An artistic impression of IceMole worming its way through solid ice. FH Aachen

The pencil-shaped craft is designed to autonomously deploy and dig itself into ice. By differentially heating parts of its tip, the robot can change direction. During its first trial run, IceMole moved at a leisurely 30 centimetres per hour, but the team says that optimal conditions would allow it to travel at more than three times that speed.

The robot houses its own internal power generator and is attached by means of a cable to a computer at the surface, which collects data. In its recent test, IceMole carried an off-the-shelf camera, but the team is designing fluorescence biosensor detectors that could search for organic molecules in the ice during its next trial run, scheduled for the summer of 2012. The probe will convey sensors in five containers running behind it, tethered together like the cars of a train. These canisters can be jettisoned on command, to seize the walls of the melted channel and be placed in specific locations.

Sterile sampling

The team hopes to eventually work with other researchers that would use IceMole to drop sensors deep in icy environments. "We like are engineers building a spacecraft; we need some scientists to build the payload," says Dachwald.

Already, a French team has expressed interest in using the probe to search for micrometeorites in ice, he says. Because it uses no external fluids to aid its movement through the ice, the robot could prove to be an ideal tool for sampling sub-glacial lakes in Antarctica while minimizing the risk of contamination from the surface, says Ryan Bay, a physicist at the University of California in Berkeley who works on the IceCube Neutrino Observatory at the South Pole and who co-organized the 2011 Antarctic Science Symposium. The IceMole team is working on a sterilization method that would drive the whole probe through a bath of hydrogen peroxide before deployment.

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Beyond Earth, the robot could drill into the martian ice caps, searching for clues about the planet's climate history or signs of life, past or present. Because it can bore through dirty ice, IceMole might also be useful on comet missions to investigate their porosity and chemical makeup, says Dachwald. Ultimately, the team's design could be used on a probe headed for icy outer moons such as Europa and Enceladus to ferret around for indications of sub-surface water and living organisms.

The device's capabilities have impressed other researchers. "It's a nice little design," says Wayne Zimmerman of NASA's Jet Propulsion Laboratory in Pasadena, California, who was the lead engineer on Cryobot, a heated ice probe that also has planetary scientists thinking about ways to explore some of the solar system's iciest environments. But Zimmerman cautions that any space-based missions would be likely to require design changes, such as building a smaller, lighter and more independent probe, to accommodate launch and landing on a distant surface.

"Making the transition from terrestrial testing to planetary exploration is a leap and a bound," he says.