Scientists Find an Underground Cave on the Moon That Could Shelter Future Explorers

Radar data from NASA’s Lunar Reconnaissance Orbiter (LRO) points to the presence of a cave beneath the moon’s surface. Such caves could serve as shelters for future human explorers, since they could protect astronauts from the moon’s hazardous surface environment, researchers report Monday in the journal Nature Astronomy.

The cave leads from a pit in the Sea of Tranquility, where Neil Armstrong and Buzz Aldrin first walked on the moon in 1969.

“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,” Katherine Joy, a planetary scientist at the University of Manchester in England who was not involved in the research, tells the Guardian’s Ian Sample. “However, we currently know very little about the underground structures below these pit entrances.”

Researchers have debated whether the moon has caves for at least 50 years. Such caves are thought to be lava tubes formed by volcanic processes billions of years ago. And some pits on the surface could be skylight-like entrances to the lava tube system below. The LRO’s camera first confirmed the presence of pits that could potentially lead to caves in 2012.

Launched in 2009, the LRO was conceived to create a 3D map of the moon, and it still orbits the moon to this day. While researchers have detected more than 200 lunar pits at this point, they previously hadn’t determined whether any led to caves.

“This research demonstrates both how radar data of the moon can be used in novel ways to address fundamental questions for science and exploration and how crucial it is to continue collecting remotely sensed data of the moon,” study co-author Wes Patterson, a planetary geologist at Johns Hopkins University, says to the Independent’s Andrew Griffin. “This includes the current LRO mission and, hopefully, future orbiter missions.”

For the new study, the researchers looked at a pit in the Sea of Tranquility that was first discovered in 2009 and is the deepest known pit on the moon. At its widest, the pit’s cylindrical hole on the lunar surface stretches more than 300 feet across. Its walls slope down before becoming nearly vertical, and its floor sits 410 feet below the surface on its west side and 443 feet deep on its east side.

The researchers used radar images taken in 2010 to find evidence of the cave connected to the pit. They estimate the initial part of the cave is at least 130 feet wide and tens of yards long or more, according to Marcia Dunn of the Associated Press (AP).

“It’s really exciting. When you make these discoveries and you look at these images, you realize you’re the first person in the history of humanity to see it,” Leonardo Carrer, a co-author of the study and researcher at the University of Trento in Italy, tells BBC News’ Georgina Rannard.

Studying the moon’s underground caves could give researchers a better understanding of how volcanism works, per the study. And by finding more pits, researchers could identify the best locations for setting up lunar bases shielded from cosmic radiation and the surface’s wide-ranging temperatures.

Other researchers warn this particular cave could be difficult to enter and exit.

“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 on to anyone below,” Robert Wagner, a research specialist at Arizona State University who did not contribute to the findings, tells the Guardian. “It’s certainly possible to get in and out, but it will take a significant amount of infrastructure.”

Astronauts might need to use “jet packs or a lift” to get out of the cave, Helen Sharman, the first British astronaut to travel to space, says to BBC News.

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Will Sullivan is a science writer based in Washington, D.C. His work has appeared in Inside Science and NOVA Next.