Challenged to probe under Greenland's glaciers, NASA robotics expert Alberto Behar wondered what mechanism might endure sub-zero cold, the pressure of mile-thick ice and currents that sometimes exceed the flow rate of Niagara Falls. As Dr. Behar at the Jet Propulsion Laboratory soon discovered, though, there isn't much money for global-warming experiments in Greenland... Unfazed, he thought of one device that might survive such extremes at a cost his field expedition could readily afford — a two-dollar rubber duck. Each duck was imprinted with an e-mail address and, in three languages, the offer of a reward.