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Going Deep

NASA's rovers currently drill mere millimeters to centimeters, but future missions may explore the solar system's subterranean ice and seas, requiring the ability to drill deep. Jupiter's Europa, for example, may be covered in liquid salt water—and if that's the case, it could also be home to some aquatic aliens. But that water is capped with a layer of ice. To get through it, a probe would need a drill that plunges dozens or maybe hundreds of meters and uses extremely little power. "It would have to use as little power as possible—just a few watts—and be completely autonomous," Gorevan says.



Honeybee has a drill design it thinks could work. It's called the Inchworm because of the way it moves: It clamps onto the sides of the borehole as it drills, then lowers itself into the space it created below and drills again. One of the questions now is how to clear debris from the hole. A derrick is too bulky to launch, and an auger, like you'd find on an ordinary electric drill, is impractical—it would have to be dozens of meters long to reach outside of the hole. Ideas the engineers are considering include flushing the debris out or shuttling it by walking the drill up and down the borehole.



If the drill were to go deeper than 300 feet, having a long tether back to the spacecraft would be unwieldy. Instead, the drill could get its power from an internal radioisotopic thermoelectric generator and venture out on its own.



That kind of low-power drilling isn't practical, or necessary, on earth, where power is easier to come by. But some of the innovations in robotic deep drills do have earthly significance. The multinational mining company Rio Tinto has approached Honeybee with interest in autonomous drilling robots. The robots would be outfitted with suites of sensors for real-time monitoring and analysis of potential new mining sites.