(First in a three-part series.) SUMMIT STATION, Greenland -- The midnight sun is shining on the Greenland ice sheet, and Yeti Robot is out for a spin.

The probe's chunky tires crunch a trail through the snow, then jerk to a stop. A blue plastic sled carrying a ground-penetrating radar crashes into Yeti's boxy black chassis, still tied to the robot by nylon ropes.

Yeti's handlers try to diagnose the problem. The robot is swinging too wide on its right turns, straying from the path programmed into its onboard GPS. The engineers confer. Seconds later, Yeti is again whizzing toward the horizon.

It's the first day of this year's field tests, and the researchers are eager to show off their prize pupil. If all goes well, battery-powered Yeti and its close relative -- a solar-powered version called Cool Robot -- could one day expand scientists' access to Earth's poles and enhance their ability to study how climate change is speeding the melt of Greenland's ice sheet.

The robots are part of a new breed of autonomous rovers, submarines, ocean gliders and unmanned aircraft designed to go places scientists can't, to handle jobs that are too dangerous or too costly for researchers to undertake themselves. ...

"If you see a crevasse, you have a couple of seconds to stop the vehicle," said Laura Ray, a professor at Dartmouth's Thayer School of Engineering who helped create Yeti and Cool Robot. "As you can imagine, that's a fairly fatiguing, stressful job."

Ray and her colleagues say Yeti could help make those supply treks safer. The robot, outfitted with a ground-penetrating radar, could take over the job of scouting for crevasses -- and interpret those data on the fly. The current version of Yeti is constructed from $25,000 worth of parts, including military-rated, ultralight batteries that can travel 10 to 15 kilometers before they need to be recharged.