Scientists have found a tunnel under the moon's surface.
The rare discovery appears to confirm the many speculations about caves that might lie beneath the lunar surface.
Now scientists have found what appears to be an underground cave. This marks the first time researchers have confirmed an accessible cave, likely a tube left by lava that has flowed beneath the moon's surface.
The data was actually collected in 2010, as part of NASA's ongoing mission for the Lunar Reconnaissance Orbiter.
But years after, researchers re-analyzed that data with new signal processing techniques, and found that this suggested there was an "underground cave conductor."
The work is published in a new paper, "Radar evidence of an accessible cave channel below the Mare Tranquillitatis pit," in the journal Nature Astronomy.