CNN
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Scientists have long theorized the existence of lunar caves – underground passages formed through volcanic processes associated with pits that cover the surface of the moon. Now, an international team of researchers has found the first direct evidence that the deepest known crater on the moon is connected 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 to create a long-term human presence. to the nearest natural satellite of the Earth.
To find the cave, the team studied archival radar measurements of a sinkhole found in a vast field called the Mare Tranquillitatis, or Sea of Tranquility, which was the landing site for the Apollo 11 mission in 1969.
NASA’s Lunar Reconnaissance Orbiter collected radar data in 2010 using wavelengths to find out what was below the surface. Analyzing the data, the researchers found empty space at a subsurface depth of 130 to 170 meters (426 to 558 feet), according to their study published Monday in the journal Nature Astronomy.
The newly discovered cave, measuring at least 45 meters (roughly 148 feet) wide and between 30 and 80 meters (98 and 262 feet) long, may just be the beginning of a longer lava tube cavity – and there are likely more Caves have yet to be found, researchers say.
“The lunar caves have remained a mystery for a long time. Scientists assumed their existence for more than 50 years. So it was surprising to finally be able to prove the existence of an underground channel,” 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. an email.
Future research and exploration of lunar caves could also provide new insight into the evolution of the moon and lunar volcanism, the study authors point out.
“The caves are a unique environment that preserves the history of the Moon,” study co-author Lorenzo Bruzzone, a telecommunications professor and director of the Remote Sensing Laboratory at the University of Trento, said via email. “Analysis of the rocks within these caves may enable new (discoveries) related to lunar evolution … such as the timeline and duration of lunar volcanic activity as well as the current composition of the lunar mantle.
“Furthermore, (lunar caves) could be an alternative or an integration for a base on the surface of the moon,” he added.
Near the moon’s equator, temperatures average 250 degrees Fahrenheit (121 degrees Celsius) in daylight and drop to minus 208 F (-133 C) at night, according to NASA. Harsh temperatures have even dipped below minus 410 F (-246 C), as recorded by the Lunar Reconnaissance Orbiter.
Researchers of a July 2022 study that looked at a number of craters on the moon — some that were assumed to lead to caves by NASA after the discovery — found that the shaded shelters are much more thermally stable, staying steadily at about 63 F ( 17C).
“Having additional evidence of a cave extending from the floor of the Mare Tranquillitatis Pit is really exciting,” said Tyler Horvath, a doctoral student in planetary science at the University of California, Los Angeles, who was the lead author of the 2022 study. email.
“Lunar caves could offer massive benefits to astronauts and rovers as they could seek shelter from hazards on the lunar surface such as radiation, micrometeorites and temperature extremes, which could also open the door to long-term, large-scale human presence on the Moon.” ,” 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 it’s likely that only a small fraction lie in caves, Horvath said. Some of the lava tubes may also be inaccessible due to debris blocking passageways, Carrer added.
The interior features of the newly discovered cave will remain unclear until a rover or human exploration can provide more insight. The inside may look similar to a recently formed lava tube on Earth, but much larger, Horvath said. This would likely have appeared as smooth walls, except where the dripping lava may have formed bumps and ridges known as lavas, and the cave would have been dark except when sunlight reached and reflected off the floor. of the crater, added Paul Hayne, an associate professor in the 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 effects this can have on the stability of lava tubes, with larger caves forming with less risk of collapse, Hayne said. who is a co-author of the 2022 study but was not involved in the new research. Most of Earth’s lava tubes are found in Hawaii, the Canary Islands, Australia and Iceland and range from 33 to 98 meters in diameter. An August 2020 study had suggested that lava tubes on the Moon could reach 1 kilometer (3,280.84 feet) in diameter.
“We shouldn’t be too surprised if future exploration reveals even bigger caves. We’re getting a glimpse of the Moon’s internal hydraulic volcanic system,” Hayne said in an email.
The authors of the new study found that the cave is potentially flat or inclined at a maximum angle of 45 degrees, suggesting it is likely accessible, Carrer said.
But because of the depth of this cave (and potentially other lunar caves), it may take some creativity to get astronauts down to the floor of the pit—perhaps including the use of rock-climbing equipment like ropes and belay devices and more cables. large 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 deep Mare Tranquillitatis crater and the newly discovered cave inside include a robotic crane that could be used to lower an astronaut or rover down to the floor, which is currently being explored 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 field. He recommended looking up and looking at the country on July 20 to celebrate the 55th anniversary of the landing of Apollo 11, the first mission to put men on the moon.
“The discovery of (possible sinkholes 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 the project scientist for both 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 included in the new study.
“LRO has been on the moon now for 15 years, creating some incredible data sets that are changing our view of the moon and being 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.”