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.
It was a daunting engineering proposition, even for someone experienced in conceiving robot explorers suitable for Mars and the moons of Jupiter.
Worried about climate change, many researchers are eager to learn how rising temperatures may be undermining Greenland's ice cap where, according to recent satellite measurements, glaciers are melting much faster than expected.
Should Greenland's 2.17 million square miles of ice ever melt completely, the water could raise sea level world-wide by 24 feet, swamping coastal cities that are home to millions of people.
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.
Consequently, Dr. Behar and his colleagues at the University of Colorado this past August released 90 yellow rubber ducks into the melt water flowing down a chasm in the largest of Greenland's 200 glaciers — the Jakobshavn Isbrae — which has been thinning rapidly since 1997.
Each duck was imprinted with an e-mail address and, in three languages, the offer of a reward.
If all goes well, Dr. Behar hopes that one day they will emerge 30 miles or so away at the glacier's edge in the open water of Disko Bay near Ilulissat, bobbing brightly amid the icebergs north of the Arctic Circle, each one a significant clue to just how warming temperatures may speed the glacier's slide to the sea.