Entering a lunar lava tube

The Moon's surface is covered by millions of craters, but it also hosts hundreds of very steep-walled holes known as pits. Like doorways to the underworld, photos of some pits clearly show a cavern beneath the Moon's surface, suggesting that they are 'skylights' into extensive lava tubes that can be as wide as New York's Central Park, and could extend for hundreds of kilometres. These tubes are thought to have formed during lava flows billions of years ago, when the Moon was still geologically active.

ESA is working on plans for a mission to explore lunar lava tubes, which could be vital in our future exploration of the Moon. Not only could they provide shelter for human visitors – shielding astronauts from radiation and micrometeorites, they may also provide access to icy water and other resources trapped underground.