On Monday, 15th July 2024, an Italian-led team of scientists claimed that there is evidence of a sizable underground cave, accessible from Mare Tranquilitatis, or the Sea of Tranquility, which is the deepest known pit on the moon.

“Lunar caves have remained a mystery for over 50 years. So it was exciting to be able to finally prove the existence” of one, Leonardo Carrer and Lorenzo Bruzzone of the University of Trento told The Associated Press in an email.

Considering it can be accessed from the surface, the site is an ideal place to establish a future lunar outpost. It would provide a natural defense against the harsh lunar atmosphere. The confirmed one is rather near the area of the 1969 landings by Neil Armstrong and Buzz Aldrin. The Mare Tranquillitatis pit, the deepest known hole on the moon, leads to a cave that is up to 80 meters long and 45 meters broad, or the equivalent of 14 tennis courts, according to radar data collected by NASA's lunar reconnaissance orbiter (LRO). The depth of this cave is around 150 meters below the lunar surface.

Underground cave
Image Source: NASA Science

Leonardo Carrer, the study's first author, said, "The main advantage of caves is that they make available the main structural parts of a possible human base without requiring complex construction activities."

According to Bruzzone, the hole was formed by the collapse of a lava tube, just like more than 200 other pits that have been found on the moon. Lava tubes are large underground tunnels formed by volcanic activity, and they have been of interest since lunar orbiters first spotted pits on the moon more than a decade ago. Many of these pits are believed to be skylights connecting to such lava tubes. For the first time, evidence of a sizable subterranean cave on the Moon has been discovered by scientists. The cave is thought to be an abandoned lava tube by researchers.

As quoted in reports, Lorenzo Bruzzone, professor at the University of Trento, explained: "These caves have been theorized for over 50 years, but it is the first time that we have demonstrated their existence." Explaining further, Bruzzone said, "In 2010, as part of the ongoing LRO NASA mission, the Miniature Radio-Frequency (Mini-RF) instrument acquired data that included a pit in Mare Tranquilitatis."

"Years later we have reanalyzed these data with complex signal processing techniques we have recently developed, and have discovered radar reflections from the area of the pit that are best explained by an underground cave conduit," he added.

There are various advantages to using these caverns as possible moonbases or emergency shelters. They offer naturally occurring defense against solar radiation, cosmic rays, and micrometeorites, and the temperature within is comparatively constant. The bottom of the Mare Tranquilitatis pit was covered in stones up to ten meters broad in earlier LRO pictures. It remained unclear, nevertheless, if the hole served as the entrance to a subterranean cave or as a stand-alone building.

Potential of Lunar Underground Caves

“Lunar cave systems have been proposed as great places to site future crewed bases, as the thick cave ceiling of rock is ideal to protect people and infrastructure from the wildly varying day-night lunar surface temperature variations and to block high energy radiation which bathes the lunar surface,” said Katherine Joy, professor in earth sciences at the University of Manchester. “However, we currently know very little about the underground structures below these pit entrances.”

The researchers also said that they analyzed radar data from NASA's Lunar Reconnaissance Orbiter (LRO) and compared the findings with Earth's lava tubes in a paper published in the journal Nature Astronomy. The experts conclude that the radar data only show the first portion of the subsurface hollow. They calculated that it is tens of yards (meters) long and at least 40 meters (130 feet) broad.

Furthermore, the experts believe that the majority of the pits are situated on the old lava plains of the moon. Additionally, there could be some in the south pole of the moon, where NASA intends to land astronauts later this decade.

There are said to be permanently shadowed craters that contain frozen water that might be used as rocket fuel and drinking water. Space organizations are thinking about how to evaluate the structural stability of these caverns and how to fortify their ceilings and walls as they get ready for people to return to the moon. Precautions will need to be taken, such as monitoring systems to identify movement or seismic activity and astronaut-designated safe areas.

Robert Wagner, a researcher at Arizona State University, said one of the biggest challenges would be access. “Getting into that pit requires descending 125 meters before you reach the floor, and the rim is a steep slope of loose debris where any movement will send little avalanches down onto anyone below,” he said. “It’s certainly possible to get in and out, but it will take a significant amount of infrastructure.”

The Italian Space Agency provided some funding for the investigation. La Venta Geographic Explorations APS and University of Padua scholars were also participating. The geological analysis and conduit modeling were enhanced by the contributions of the researchers.

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