by Scientists have long theorized about the existence of moon caves — underground passages formed by volcanic processes that are connected to the pits that cover the moon’s surface. Now, a team of international researchers has found the first direct evidence that the deepest hole on the moon connects to a cave that could provide shelter for astronauts.
Areas on the moon that can protect humans and robotic explorers from the harsh lunar environment — including powerful radiation and extreme temperatures — could be vital for future space exploration and countries like the United States and China race to establish a long-term human presence. the closest natural satellite to Earth.
To find the cave, the team studied archival radar measurements of a pit found within a large plain known as Mare Tranquillitatis, or Sea of Tranquility, which was the landing site for the Apollo 11 mission in 1969.
NASA’s Lunar Reconnaissance Orbiter collected the radar data in 2010 using wavelengths to detect what was below the surface. Analyzing the data, the researchers found empty space at a depth underground of 130 to 170 meters (426 to 558 feet), according to their study published Monday in the journal Nature Astronomy.
The newly revealed cave, which measures at least 45 meters (almost 148 feet) wide and between 30 and 80 meters (98 and 262 feet) long, may be just the beginning of a longer tube cavity. by lava — and there’s probably more. caves still to be found, researchers say.
“Moon caves have long been a mystery. Scientists hypothesized to exist from more than 50 years. So it was surprising to finally be able to create a subsurface conduit,” 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.
Research and exploration of lunar caves in the future could also provide new insight into the evolution of the moon and lunar volcanism, according to the authors of the study.
“The 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 the University of Trento, said by email. “The analysis of rocks inside these caves could enable new discoveries related to the evolution of the moon … such as the timeline and duration of lunar volcanic activity as well as the actual composition of the lunar mantle.
“Furthermore, (lunar caves) can be an alternative or an integration to a base on the lunar surface,” he said.
Using moon caves as shelter
Near the moon’s equator, the average temperature reaches a blistering 250 degrees Fahrenheit (121 degrees Celsius) in daylight and drops to minus 208 F (-133 C) at nightfall, according to NASA. The harsh temperatures have even dropped below minus 410 F (-246 C), as recorded by the Lunar Reconnaissance Orbiter.
A July 2022 study by researchers who looked at several pits on the moon – some of which were hypothesized to have led NASA into caves when they were discovered – found that the shaded shelters are much more thermally stable and that they remain constant at about 63 F (17 C). ).
“It’s really exciting to have additional evidence of a cave extending from the floor of the Mare Tranquillitatis Pit,” said Tyler Horvath, a doctoral student in planetary science at the University of California, Los Angeles, who was lead author of the 2022 study, i. email.
“Moon caves could provide huge advantages for astronauts and rovers as they can seek shelter from the hazards on the lunar surface such as radiation, micrometeorites, and temperature extremes, which could also open the door to presence human on a large scale in the long term. Moon,” Horvath said. He was not involved in the new study.
The moon has more than 200 known pits like the one at Mare Tranquillitatis, but probably only a handful lead to caves, Horvath said. Some of the lava tubes may also be inaccessible due to debris blocking the passages, Carrer added.
The interior features of the newly discovered cave will not be clear until a rover or human exploration can provide more insight. The interior may be similar to a recently formed lava tube on Earth, but much larger, Horvath said. This would probably look like smooth walls except where flowing lava could create bumps and ridges called lavacicles, and the cave would be dark, except when sunlight reaches and reflects off the floor of the pit , said Paul Hayne, associate professor in. department of astrophysical and planetary sciences at the University of Colorado, Boulder.
The large size of the cave is not surprising, given the moon’s lower gravity and the effect this may have on the stability of the lava tubes, with larger caves able to form and less risk of collapse, Hayne said. , of which he is a co-author. 2022 study but was not involved in the new research. Most of the World’s lava tubes are found in Hawaii, the Canary Islands, Australia and Iceland, and are between 33 and 98 feet in diameter. A study in August 2020 suggested that lava tubes on the moon could reach 1 kilometer (3280.84 feet) in diameter.
“We shouldn’t be too surprised if future exploration reveals even bigger caves. We are gaining insight into the Moon’s internal volcanic plumbing system,” Hayne said in an email.
Future exploration of lunar caves
The authors of the new study found that the cave could be flat or tilted at an angle of up to 45 degrees, suggesting it was likely accessible, Carrer said.
But because of the depth of this cave (and other possible moon caves), it may take some creativity to get astronauts down to the floor of the pit – possibly using climbing gear rock as ropes and belay devices and larger cables for equipment and construction materials, Hayne said. Eventually, the process could involve a more permanent structure, such as a freight elevator, he said.
Other ideas for exploring the Mare Tranquillitatis deep hole 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 explored by the Space Agency of Europe.
Noah Petro, chief of NASA’s Planetary Geology, Geophysics and Geochemistry Laboratory, noted that moon-gazing astronomers can identify Mare Tranquillitatis, where the cave was discovered, by looking for a large, dark plain. He suggested looking up and looking at the site on July 20 to celebrate the 55th anniversary of the landing of Apollo 11, the first mission to put humans on the moon.
“The discovery of (potential pits and caves) goes 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 project scientist for the Lunar Reconnaissance Orbiter and Artemis III, a 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.
“LRO has now been on the moon for 15 years, creating some incredible data sets that are changing our perspective on the moon and using them to make these discoveries,” said Petro. “(The cave) is one of those great surprises that the moon always has for us.”
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