US and Italian researchers have found evidence of potentially accessible underground cave networks on the Moon, that could offer a potential shelter for future crewed missions to the lunar surface. They say that over 200 pits have been found on the surface, with many having been created by cave-ins from lava having flowed underneath. One of these pits, known as the Mare Tranquillitatis Pit, has a radius of around 100 metres, and the researchers say their simulations based on radar images suggest the potential for a tunnel located between 130 and 170 metres deep, between 30 and 80 metres long, and with a width of around 45 metres.
Journal/conference: Nature Astronomy
Link to research (DOI): 10.1038/s41550-024-02302-y
Organisation/s: University of Trento, Trento, Italy
Funder: This work was supported by the Italian Space
Agency (Contract No. 2022-23-HH.0, ‘Attività scientifiche per il radar
sounder di EnVision fase B1’).
Media release
From: Springer Nature
 Potentially accessible cave conduit revealed under Moon’s landscape
Evidence of a potentially accessible, underground cave conduit originating from an open pit on the Moon is reported in a Nature Astronomy paper. The findings provide insights on lunar geology and its role in potentially offering shelter for future crewed missions to the Moon’s surface.Â
More than 200 pits have been found on the Moon’s surface, some of which, dubbed ‘skylights’, are formed by cave-ins of an underlying lava tube. Accessible lava tubes or conduits could provide a more temperate environment than the surface. However, whether they provide access to caves with large underground volumes is uncertain.
Leonardo Carrer, Lorenzo Bruzzone, and colleagues analysed radar data from the Lunar Reconnaissance Orbiter of the Mare Tranquillitatis Pit — the deepest known pit on the Moon, with a radius of approximately 100 metres, vertical or overhanging walls and a sloping floor. The authors observed an increase in radar brightness on the west side of the pit. Using simulations based on the radar images, they conclude that these observations can be explained by the presence of a cave void or conduit expanding from the west side of the pit bottom. The scientists  estimate that the conduit is located at a depth of 130–170 metres and is between 30–80 metres long and around 45 metres wide. The cave is also potentially flat or inclined by a maximum of 45 degrees and is likely accessible.
The authors suggest that volcanic tubes or conduits could be a common feature under the lunar plains, and that the Mare Tranquillitatis Pit and its conduit could be a promising site for a potential lunar base. The methodology presented could also be a viable option for assessing and characterising other lunar pits to identify additional conduits.