Since 2009, NASA’s Lunar Reconnaissance Orbiter (LRO) has spotted hundreds of conspicuous holes on the Moon. These steep-walled “pits" vary from a few meters to nearly 1 kilometer wide, and can reach depths of over 100 meters. Scientists think that pits may form when part of the Moon’s surface collapses above a lava tube, and high-resolution photographs from LRO suggest that many of the pits widen underground. If so, lunar pits might provide shelter from radiation, meteorite impacts, and extreme temperatures, making them valuable sites for future exploration.