Interest in the moon's south pole grew last year when India's Chandrayaan-3 mission made the first effective touch-and-go approach nearby, just days after Russia's Luna-25 rocket crashed while transiting to attempt a similar feat. NASA has selected the site as the landing site for its Artemis III mission, which could check the arrival of space explorers on the moon in 2026, and China also has plans to create future environments there.
In any case, for now, a NASA-backed review warns: As the center of the moon cools step by step and psychologists, its surface develops wrinkles — like grapes wilting in a raisin — that cause "moon tremors" that can last for a long time. for a long time, as well as avalanches. Like the rest of the surface of a regular satellite, the South Pole region of such interest is prone to these seismic peculiarities, which may pose a hazard to future human travelers and equipment.
"This is not to alert anybody, and certainly not to surpass the investigation of that piece of the south pole of the moon," said the review's lead author Thomas R. Watters, scientist emeritus at the Public Air and Space Gallery's Middle. for Earth and Planetary Examinations, "further to heighten vigilance that the Moon is not a harmless place where nothing happens."
Tracing the source of the moonquakes
The moon has shrunk by about 150 feet in circumference over the past barely a million years — a huge number in geographical terms, but too little to create any far-reaching effects on the planet or on the ongoing cycles, experts say.
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"There's an inner layer that's liquid and cools," Watters said. "As it cools, the Moon recedes, the internal volume changes, and the mantle has to adapt to this change - it's a global pullback that also contributes to the flow forces on Earth."
Because the Moon's surface is brittle, this tug creates cracks that geologists call flaws. "The moon is thought of as this geographically dead link where nothing has happened for billions of years, yet that couldn't be further from the truth," Watters said. "These flaws are exceptionally young and things are happening. We actually identified avalanches that happened during the time the Lunar Surveillance Orbiter was orbiting the Moon."
NASA's Lunar Observation Orbiter, or LRO, was launched in 2009 and surveys the surface of the moon using a variety of instruments. In a new review, distributed Jan. 25 in The Planetary Science Diary, Watters and his partners used information collected by LRO to link a strong lunar earthquake — detected by instruments left behind by Apollo space travelers some time ago — to the progression of faults in the moon's south pole.
"We knew from the Apollo seismic survey, which was four seismometers that ran for about seven years, that there were these shallow moonquakes, but we didn't really have the foggiest idea what the source was," Watters added. "Additionally, we knew that the largest of the shallow lunar tremors detected by the Apollo seismometers was located near the South Pole. It turned into a kind of story of a criminal investigator trying to find out what the source was, and by the way, these juvenile flaws are the best suspect ."
The most ground shaking recorded was what would equate to a magnitude of 5.0. It would be considered mild on the planet, but the moon's lower gravity would make it worse, Watters said.
"On Earth, you have a much more grounded gravity that keeps you connected to the surface. On the Moon, it's much more modest, so even a small increase in ground speed might lift you off your feet, if you're not kidding," he said. "That kind of shaking can really start throwing things around in a low-G climate."
Moon tremors: Transient versus long tracks
The review's findings will not affect the Artemis III landing site determination cycle, due to the stage and timing of the mission, as indicated by the focus on co-author and NASA planetary researcher Renee Weber.
"This is because it is difficult to accurately assess how often a particular area will experience a monthly earthquake, and like earthquakes, we cannot predict monthly earthquakes," Weber said. "Fixed shallow moonquakes are inconsistent and represent generally safe to transient missions on the lunar surface."
NASA recognized 13 Artemis III competitor landing areas near the lunar south pole, supplied using measures such as the ability to land safely in place, the ability to meet science objectives, window accessibility, and conditions such as territory, correspondence, and lighting. As part of the mission, the two space explorers will spend about seven days living and interacting with the lunar surface.
Regardless, Weber said, in the event of a long human presence on the moon, the site selection cycle could confidently calculate geographic qualities such as proximity to structural features and landscapes.
Like electric lamps on the moon
Lunar tremors could certainly be a problem for future monitored landing missions, said Yosio Nakamura, professor emeritus of geophysics at the University of Texas at Austin, who was among the specialists who initially examined the information collected by the Apollo seismic stations.
In any case, Nakamura, who was not involved in the inspection, differs on the reason for the tremors, saying the Apollo information shows the oddities start several kilometers below the surface.
"We actually don't have the foggiest idea what causes shallow lunar tremors, but it's not a near-surface sliding problem," he said. "Regardless of what's causing these tremors, the facts really confirm that they pose a potential hazard to future landing missions, and we want more information about them."
Whatever the underlying reason, the potential risk of lunar shocks to space travelers will be limited by how — soon — humans will be on the moon for a short period of time, a few days, all things considered, according to Allen Husker, research. geophysics teacher at the California Organization of Innovation, who was also not involved in the review.
"It's far-fetched that there will be a huge moonquake when they're there. In any case, it's great to know that these seismic sources (causing tremors) exist. They can be a wonderful opportunity to focus more easily on the moon, as we do on Earth in an earthquake," Husker said. "Once there's an actual lunar base, we should have a much better idea of the actual seismic risk with upcoming missions.
This sentiment is shared by Jeffrey Andrews-Hanna, an academic administrator for planetary science at the College of Arizona, who was also not involved in the work. "Moonquakes are an amazing tool for science," he said in an email. "They resemble electric lamps in the lunar interior that illuminate its design so we could see. Examining the moon's south pole tremors really informs us about the moon's internal structure as well as its current activity."
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