article_snippet: This was thanks to the low gravity of the moon 3.5 billion years ago .
article_snippet: Scientists believe there is a huge network of tunnels that exist beneath the lunar surface.
article_snippet: Now a  study by Durham University has claimed that tubes 0.6 miles (1km) in diameter could be stable enough to house permanent bases beneath the lunar surface.
article_snippet: Researchers believe that these lava tubes could help protect future astronauts against the challenges of the harsh lunar environment, which lacks a thick atmosphere.
highlights_snippet: This was thanks to the low gravity of the moon .
  