CNN
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Scientists have long theorized about the existence of lunar caves – underground passages created by volcanic processes that are connected to pits covering the surface of the moon. Now, a team of international researchers has found the first direct evidence that the deepest known pit on the moon connects to a cave that could provide shelter for astronauts.
Identifying areas on the moon that can protect humans and robotic explorers from the harsh lunar environment — including intense radiation and extreme temperatures — could be crucial to future space exploration as countries like the United States and China race to establish a long-term human presence. to the nearest natural satellite of Earth.
To find the cave, the team studied archival radar measurements of a pit found in a vast plain called the Mare Tranquillitatis, or Sea of Tranquility, which was the landing site of the Apollo 11 mission in 1969.
NASA’s Lunar Reconnaissance Orbiter collected radar data in 2010 using wavelengths to detect what was below the surface. Analyzing the data, the scientists found an empty space 130 to 170 meters (426 to 558 feet) underground, according to a study published Monday in the journal Nature Astronomy.
The newly discovered cave, which measures at least 45 meters (nearly 148 feet) wide and between 30 and 80 meters (98 and 262 feet) long, could be just the beginning of a longer lava tube cavity — and there are likely more. the caves have not yet been found, researchers say.
“The Moon Caves remained a mystery for a long time. Scientists have assumed their existence for more than 50 years. So it was surprising that we could finally demonstrate the existence of subsurface conduction,” study co-author Leonardo Carrer, an assistant professor in the department of information engineering and computer science at the University of Trento in Italy, said in an email.
Future research and exploration of lunar caves could also provide new insights into the evolution of the Moon and lunar volcanism, the authors note in the study.
“Caves are a unique environment that preserves the history of the Moon,” study co-author Lorenzo Bruzzone, professor of telecommunications and director of the Remote Sensing Laboratory at Trent University, said via email. “Analysis of the rocks inside these caves could allow new (discoveries) related to lunar evolution … such as the timeline and duration of lunar volcanic activity, as well as the actual composition of the lunar mantle.
“In addition, (lunar caves) can be an alternative or integration to a base on the surface of the moon,” he added.
Near the lunar equator, temperatures average 250 degrees Fahrenheit (121 degrees Celsius) during daylight and drop as low as -133 C (208 F) at dusk, according to NASA. Harsh temperatures even dropped below minus 410 F (-246 C), as recorded by the Lunar Reconnaissance Orbiter.
Researchers in a July 2022 study that looked at a series of dimples on the moon — some of which were assumed by NASA to lead to caves after their discovery — found that shaded shelters are much more thermally stable, staying steadily around 63 F (17 C). ).
“Having more evidence of a cave protruding from the floor of the Mare Tranquillitatis Pit is really exciting,” Tyler Horvath, a doctoral student in planetary sciences at UCLA who was the lead author of the 2022 study, said in an email.
“Moon caves could provide huge advantages for astronauts and rovers as they can seek shelter from hazards on the lunar surface such as radiation, micrometeorites and temperature extremes, which could also open the door to a long-term large-scale human presence on the lunar surface.” A month,” Horvath added. He was not involved in the new study.
The moon has more than 200 known craters like the one in Mare Tranquillitatis, but probably only a handful are caving in, Horvath said. Some of the lava tubes could also be inaccessible due to debris blocking the passages, Carrer added.
The interior features of the newly discovered cave will remain unclear until rover or human exploration provides more information. The interior may appear similar to a recently formed lava tube on Earth, but much larger, Horvath said. It would probably look like smooth walls except where the dripping lava might form bumps and ridges known as lavacicles, and the cave would be like pitch black except where sunlight would reach and reflect off the bottom of the pit, Paul Hayne added. Associate Professor, Department of Astrophysics and Planetary Sciences, University of Colorado, Boulder.
The large size of the cave is not surprising, given the moon’s lower gravity and the effects that can have on the stability of lava tubes, where larger caves can form with less risk of collapse, said Hayne, who co-authored the 2022 study but was not involved in the new research . Most terrestrial lava tubes are found in Hawaii, the Canary Islands, Australia, and Iceland and range from 33 to 98 feet in diameter. An August 2020 study suggested that lava tubes on the Moon could reach a diameter of 1 kilometer (3,280.84 ft).
“We shouldn’t be too surprised if future exploration reveals even bigger caves.” We’re getting a glimpse of the Moon’s internal volcanic plumbing system,” Hayne said in an email.
The authors of the new study found that the cave is potentially flat or tilted at a maximum angle of 45 degrees, suggesting it would likely be accessible, Carrer said.
But because of the depth of this cave (and potentially other lunar caves), it might take some creativity to get astronauts down to the bottom of the pit — which may include using climbing equipment such as ropes and belay devices and larger cables for equipment and building materials, Hayne said. Eventually, the process could include a more permanent structure, such as a freight elevator, he added.
Other ideas for exploring the Mare Tranquillitatis deep pit and the newly discovered cave inside include a robotic crane that could be used to lower an astronaut or rover to the floor, which is currently being investigated by the European Space Agency.
Noah Petro, chief of NASA’s Planetary Geology, Geophysics and Geochemistry Laboratory, noted that sky watchers observing the Moon can identify Mare Tranquillitatis, where the cave was discovered, by looking for a large dark plain. He recommended looking up to see the site on July 20 to celebrate the 55th anniversary of the landing of Apollo 11, the first mission to land humans on the moon.
“The discovery (of pits and potential caves) dates back several years (but) this new information from the radar data says, ‘Oh, wow.’ They’re a little bigger than we expected,” said Petro, who is a project scientist for both the Lunar Reconnaissance Orbiter, so for Artemis III, the mission that aims to land humans on the moon for the first time since Apollo 17 in 1972. Petro was not involved in the new study.
“The LRO has been on the Moon for 15 years and is generating incredible data sets that change our perspective of the Moon and are used to make these kinds of discoveries,” Petro said. “(The cave) is one of those wonderful surprises the moon always has in store for us.”