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A region of the Moon that is at the center of a new international space race because it may contain water ice could be less hospitable than previously thought, new research has found.
Interest in the lunar south pole increased last year, when the Indian Chandrayaan-3 mission carried out the first successful soft landing in the area, just days after the Russian Luna-25 spacecraft it crashed on the way to attempt the same feat. NASA has selected the region as a landing site for its Artemis III mission, which could mark the return of astronauts to the moon as soon as possible. 2026, and China also has plans to create future habitats there.
But now a study funded by NASA is sounding an alarm: As the moon’s core gradually cools and contracts, its surface develops wrinkles (like a grape shriveling into a raisin) that create “lunar tremors” that can last for hours, as well as landslides. Like the rest of the surface of the natural satellite, the area of the south pole that is the subject of so much interest is prone to these seismic phenomena, which potentially represents a threat to future settlers and human teams.
“This is not to alarm anyone and certainly not to discourage exploration of that part of the Moon’s south pole,” said the study’s lead author, Thomas R. Watters, a scientist emeritus at the National Air Museum’s Earth Center. and Space. and Planetary Studies, “but to warn that the Moon is not a benign place where nothing happens.”
The moon has shrunk by about 150 feet in circumference over the past few million years, a significant amount in geological terms but too small to cause any ripple effects on Earth or tidal cycles, according to researchers.
On the lunar surface, however, the story is different. Despite what its appearance may suggest, the moon still has a hot interior, making it seismically active.
“There is an outer core that is molten and is cooling,” Watters said. “As it cools, the moon shrinks, the interior volume changes and the crust has to adapt to that change; it is a global contraction, to which tidal forces on Earth also contribute.”
Because the moon’s surface is fragile, this pull creates cracks, which geologists call faults. “The moon is thought to be a geologically dead object where nothing has happened for billions of years, but that couldn’t be further from the truth,” Watters said. “These failures are very young and things are happening. “In fact, we have detected landslides that occurred during the time that the Lunar Reconnaissance Orbiter was in orbit around the Moon.”
NASA’s Lunar Reconnaissance Orbiter, or LRO, launched in 2009and is mapping the surface of the moon with various instruments. In the new study, published Jan. 25 in The Planetary Science Journal, Watters and his colleagues used data collected by LRO to link a powerful lunar earthquake (detected with instruments left by Apollo astronauts more than 50 years ago) with a series of faults on the lunar surface. South Pole.
“We knew from the Apollo seismic experiment, which consisted of four seismometers operating over a period of about seven years, that there were these shallow moonquakes, but we didn’t really know what the source was,” Watters added. “We also knew that the largest of the shallow moonquakes detected by the Apollo seismometers was located near the south pole. It became a bit of a detective story to try to figure out what the source was, and it turns out that these flawed young people are the best suspects.”
The strongest earthquake on record was the equivalent of a magnitude of 5.0. On Earth, that would be considered moderate, but the Moon’s lower gravity would make it feel worse, Watters said.
“On Earth, you have much stronger gravity that keeps you glued to the surface. On the Moon, it’s much smaller, so even a little bit of ground acceleration will potentially throw you off balance if you’re walking,” she said. “That kind of shaking can really cause things to move around in a low-gravity environment.”
The study’s findings will not affect the Artemis III landing region selection process, and that is due to the scope and duration of the mission, according to study co-author and NASA planetary scientist Renee Weber.
“This is because it is difficult to accurately estimate how often a specific region experiences a moonquake, and like earthquakes, we cannot predict moonquakes,” Weber said. “Strong, shallow lunar earthquakes are rare and pose a low risk for short-duration missions to the lunar surface.”
NASA has identified 13 candidate regions for landing on Artemis III near the lunar south pole, he added, using criteria such as the ability to land safely in the region, the potential to meet scientific objectives, the availability of launch windows and conditions such as the terrain, communications and lighting. . As part of the mission, two astronauts will spend about a week living and working on the lunar surface.
However, Weber said, for a long-term human presence on the Moon, the site selection process could actually take into account geographic features such as proximity to tectonic features and terrain.
In fact, lunar earthquakes could be a problem for future manned landing missions, said Yosio Nakamura, professor emeritus of geophysics at the University of Texas at Austin, who was among the researchers who first looked at the data collected by the seismic stations. Apollo.
However, Nakamura, who was not involved in the study, disagrees about what causes the earthquakes and said Apollo data shows the phenomena originate tens of kilometers below the surface.
“We still don’t know what causes shallow moonquakes, but it’s not the strike-slip fault near the surface,” he said. “Regardless of the causes of those earthquakes, it is true that they represent a potential threat to future landing missions and we need more data on them.”
Regardless of the underlying cause, the potential danger that moonquakes pose to astronauts will be limited by the fact that, at least in the near future, humans will be on the Moon for short periods of time, a few days at most. according to Allen Husker. , a research professor of geophysics at the California Institute of Technology who was also not involved in the study.
“It is very unlikely that a large earthquake will occur while they are there. However, it is good to know that these seismic sources (which cause earthquakes) exist. They can be an opportunity to better study the Moon like we do on Earth with earthquakes,” Husker said. “By the time there is a real lunar base, we should have a much better idea of the real seismic danger of the upcoming missions.”
That sentiment is shared by Jeffrey Andrews-Hanna, an associate professor of planetary science at the University of Arizona, who was also not involved in the work. “Moonquakes are an incredible tool for doing science,” he said in an email. “They are like lanterns in the lunar interior that illuminate its structure so that we can see it. “Studying lunar earthquakes at the south pole will tell us more about the interior structure of the Moon, as well as its current activity.”