Challenged to probe under Greenland's glaciers, NASA robotics expert Alberto Behar wondered what mechanism might endure subzero 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...