Unmanned marine robots, called autonomous underwater vehicles, can be used for myriad research purposes. The type the Woods Hole Oceanographic Institution in Massachusetts employs goes to the Arctic's icy depths.

WHOI deployed two AUVs, Puma and Jaguar, in the summer of 2007 to investigate hydrothermal vents along the seafloor in an area of the eastern Arctic Ocean called the Gakkel Ridge.

The ultra-slow-moving plates of the Earth's crust in that region produce volcanic activity and unusual interactions between the hot gases and the nearly freezing ocean water. Scientists have been eager to look at the zone's creatures, which they believe have evolved in isolation over millions of years.

During WHOI's 40-day mission to explore the mid-ocean ridge's handiwork, Puma "sniffed out" chemical and temperature signatures of the mineral-spewing vents, and Jaguar took pictures and used sonar to map the ocean floor. A tethered, remote-controlled vehicle scooped up rock samples, sediment and creatures for scientists to study.

Researchers aboard the Swedish icebreaker Oden dropped the AUVs through holes in the ice and retrieved them through other holes -- that is, unless the icepack was so compressed that the drifting sheets created no openings. In one such situation, recalled mission chief scientist Robert Reves-Sohn, the Oden had to "wiggle" around in the ice, creating just enough room around the hull to allow the AUVs to surface. "It was a very challenging activity," he noted.

WHOI's two polar AUVs were custom-made to essentially act as helicopters to travel to depths of 4,000 meters -- much deeper than their torpedo-like counterparts, Reves-Sohn said. Besides learning more about this isolated spot on Earth, the mission was aimed at testing autonomous exploration and sample-return techniques that NASA will use in its search for life in the ice-covered oceans of Jupiter's moon Europa.

-- By Larisa Epatko, Online NewsHour