"Four hours into a September 2017 Air France flight 66 from Paris to Los Angeles, one of the aircraft's four engines spontaneously exploded. 'IS THERE A PROBLEM,' read the message from air traffic controllers to the pilots. The plane, with over 500 people onboard, was flying four thousand feet below its previous altitude and, indeed, there was a problem. The front portion of an engine had fallen off, plummeting more than seven miles to the frozen Greenland ice sheet below," reports CNN.

... "The ordeal set French authorities on a years-long mission to find the lost engine pieces and pinpoint the root cause of the problem, requiring investigators to survey miles of terrain made perilous by deep, invisible cracks in Greenland's ice sheet and the constant threat of polar bear attacks. The endeavor was also hampered by months of inhospitable storms, limited daylight and low visibility. Researchers ultimately found the key piece of debris — the engine's fan — by accident, when a robot mapping glacial crevasses happened to roll over the spot where it was buried nearly two years after it had fallen from the sky, said [Dartmouth Engineering PhD student] Austin Lines, a US-based engineer who aided the recovery effort. It was packed in four meters (or about 12 feet) of snow and ice.

"Lines told CNN Business that at one point, investigators dropped a replica of the engine fan into the snow, just to make sure the radars they were using for the search could accurately detect the buried metal. But they couldn't. And for months, the replica debris was lost, too."

... "Lines, who developed a four-wheeled robot called FrostyBoy that's designed to map crevasses, was tapped by [France's Bureau of Enquiry and Analysis for Civil Aviation Safety] to help the recovery effort — but the robot ended up being the lynchpin for the entire project. While searching for cracks, the rover's sensors picked up an abnormal reading, reavealing the robot had — by pure happenstance — rolled over the engine fan's exact resting place.

"'We're ridiculously lucky that it happened the way it happened,' Lines said of FrostyBoy's chance detection. It gave his robot, a project he worked on while pursing his PhD at Dartmouth, a small but bizarre claim to fame.

"'I don't think anyone would care that much if a bunch of dudes went out with a robot and didn't do much with it,' he joked."

You can watch Dartmouth Engineering's video and read Dartmouth Engineering's article about FrostyBoy's discovery here.