50-km-long cave discovered on Moon by Japan's lunar orbiter
Japan's lunar orbiter has confirmed a 50-km-long, 100-metre-wide cave on the moon after examining the hole using radio waves. Japan's space agency JAXA believes the cave is a lava tube created during volcanic activity about 3.5 billion years ago. The lava tubes might be the "best candidate sites" for future lunar bases, to protect people from cosmic rays, said researchers.