Deep pit on moon may be entrance to cave that could act as lunar base

There is probably a network of caves hidden just below the surface of the moon, and researchers may have finally found an access point. These caves have long been predicted, but until now it has been difficult to prove their existence or find a way for future missions to explore them directly.

The surface of the moon is riddled with pits and so-called skylights, which are openings in the roof of a cave that are thought to have formed from the collapse of ancient lava tubes – tunnels formed as lava flows beneath a solid crust. Leonardo Carrer at the University of Trento in Italy and his colleagues re-analysed radar observations of the deepest known of these features, called the Mare Tranquillitatis pit, which were taken by NASA’s Lunar Reconnaissance Orbiter in 2010.

Using simulations and comparisons to lava tubes on Earth, the researchers found that the Mare Tranquillitatis pit seems to lead to a large cave buried at least 130 metres underground. The cave seems to be about 45 metres wide and at least 30 metres long, although it could be even larger.

Caves like this could provide a unique window into the moon’s evolution, says Carrer. “Analysing lunar cave rocks that are not altered by the harsh lunar surface environment can provide significant insights into key scientific questions such as the timeline and duration of lunar volcanic activity, as well as the actual composition of the lunar mantle,” he says.

The same stone ceiling that protects cave rocks from the intense radiation experienced at the surface could also provide valuable shielding to future human explorers on the moon. “Unlike the lunar surface where the temperature varies dramatically between day and night, [the caves] have a stable internal temperature. Moreover, they are also a natural shielding against radiation and impacts,” says Carrer.

Using natural caves like this one as lunar base camps has long been a popular idea, so future astronauts may one day call Mare Tranquillitatis home.