The moon's surface isn’t just full of craters — it’s also full of holes. And according to NASA, these holes, and the underground caves to which they connect, could one day provide shelter to the space agency’s astronauts.

The moon’s more than 200 holes, or "lunar pits," were discovered by NASA’s Lunar Reconnaissance Orbiter, reports Motherboard. These pits range in size from about 5 meters in diameter to more than 900 meters, and were likely formed when part of the moon’s surface collapsed over a cave. And the caves themselves may have been formed by ancient lava streams, NASA says.

"A habitat placed in a pit... would provide a very safe location."

"A habitat placed in a pit — ideally several dozen meters back under an overhang — would provide a very safe location for astronauts: no radiation, no micrometeorites, possibly very little dust, and no wild day-night temperature swings," said Robert Wagner, one of the Arizona State University researchers who helped discover the holes, in a statement.

Now that NASA has identified these caves, researchers are hoping to explore them. And according to Wagner, the best way to do so is to drop a probe into the holes. The pits, he explained, "cannot be explored very well from orbit."

In the meantime, however, Wagner and his team will continue to scan images of the moon’s craters to identify more pits. This may be difficult because "for about 25 percent for the moon’s surface area (near the holes) the sun never rises high enough for our algorithm to work," Wagner said. So, improving search algorithms may prove critical if we ever want to house astronauts on — or in — the moon.