Discovery: "When life was just emerging on Earth, streams of molten lava flowed across the moon and then solidified. Such tubes on Earth form when lava from a volcano starts to cool and form a hardened crust. Hot lava underneath continues flowing in channels.
The moon's frozen tunnels could provide a natural shelter from the extremes on the lunar surface. Assuming we decide to return to the moon someday -- it’s not on NASA’s agenda for now -- the lava tubes would allow for ant farm-like colonies of humans living underground.
The tunnels would shield colonists from micrometeorites, lethal X-ray blasts from our petulant sun, and cosmic rays from the galaxy. Temperatures inside the tubes would remain a constant -35 degrees Fahrenheit. That's chilly, but much more stable for complex equipment. On the surface, machinery and structures would degrade under temperature extremes that swing from +250 degrees to -250 during the lunar day/night cycle."