Finding the pits was no easy task. The moon's north pole has harsh lighting that makes it difficult to distinguish ordinary craters from a pit leading to an underground entrance. Lee joked that most of his searching from LRO data resulted in "pictures of high-resolution shadow." But the sun shone at just the right angle in some of the pictures, revealing the pits. Now that Lee's search hit pay dirt, he says the next step is figuring out how much ice is within the reservoirs.
More pictures from above won't really help, Lee said, because the lighting is difficult. Instead, he advocates sending a rover to the surface equipped with ground-penetrating radar. The rover could squat nearby a pit opening and use radar to image the surface below. This would show the presence — or absence — of ice.
A drone would ideally be used during a follow-up mission. Lee regularly tests drones as part of the Haughton-Mars Project, a research effort that takes place every summer on Devon Island in Canada. The researchers normally focus on technologies for human missions to Mars, but drones would work on both the moon and Mars, Lee said.
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A typical drone today is almost smart enough to navigate obstacles on its own, using artificial intelligence, he said. With a few more years of development, drones could be deployed on the moon. The drones could fly into the lava tubes, collect images and data and then fly out again to transmit the information back to a nearby lander — or back to Earth directly.
From there, Lee said there could be enough data to justify sending humans into the lava tubes to extract water and conduct experiments. Some science fiction scenarios envision humans using these tubes as shelters, but Lee said an artificial dome protected by sandbags would be a much better seal against the moon's airless environment.
There is no robot mission scheduled after the Lunar Reconnaissance Orbiter, which is in good health. But it has been orbiting the moon since 2009. NASA is recasting its lunar exploration plans after the Trump administration announced last year that they plan to send astronauts back to the moon. Luckily, NASA does have an idea to send a polar-orbiting space station to the moon called Deep Space Gateway. The space station would orbit pole-to-pole — allowing the astronauts to look at the potential lava tubes from their perch in orbit.
Lee presented his research at the Lunar Science for Landed Missions Workshop, which was convened by the Solar System Exploration Research Virtual Institute at the NASA Ames Research Center in Silicon Valley, California.