The size of the Earth’s moon is shrinking. Here’s what scientists say this could mean

(CNN) — A region of the Moon that is at the center of a new international space race because it may contain water ice may be less welcoming than previously thought, new research suggests.

Interest in the moon’s south pole surged last year, when India’s Chandrayaan-3 mission made the first successful soft landing in the region, just days after the Russian Luna-25 spacecraft was on its way attempting the same feat. Had crashed. NASA has selected the area as a landing site for its Artemis III mission, which could mark the return of astronauts to the Moon in 2026, and China also plans to build future housing there.

But now a NASA-funded study is sounding alarm bells: As the moon’s core slowly cools and contracts, wrinkles develop on its surface — like grapes shrinking into raisins — causing “lunar vibrations.” A storm is created, which lasts for hours, accompanied by landslides. Like the rest of the natural satellite’s surface, the region of the south pole that is of so much interest is prone to these seismic events, potentially representing a danger to future settlers and human teams.

The study’s lead author, scientist Thomas R. “This is not to alarm anyone and certainly not to discourage exploration of that part of the Moon’s south pole,” Waters said, “but to serve as a warning that the Moon is not a benign place.” Nothing happens.” Emeritus at the National Air and Space Museum’s Center for Earth and Planetary Studies.

Finding the source of lunar earthquakes

According to the researchers, the Moon’s circumference has decreased by about 45 meters over the past few million years, a significant number in geological terms, but too small to cause any ripple effects on Earth or tidal cycles.

However, the story is different on the surface of the Moon. Despite its appearance, the Moon’s interior is still hot, making it seismically active.

“There is an outer core that is molten and cooling,” Waters said. “As it cools, the Moon contracts, the internal volume changes and the crust has to adapt to that change; this is a global contraction, to which tidal forces on Earth also contribute.”

Since the Moon’s surface is fragile, this stretching 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,” Waters said. “These faults are very new and things are happening (there). In fact, we 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 2009 and is mapping the moon’s surface with multiple instruments. In the new study, published Jan. 25 in the journal The Planetary Science, Waters and colleagues link a series of faults to a powerful lunar earthquake (detected by instruments left by Apollo astronauts more than 50 years ago) to LRO. Used data collected by. On the lunar surface of the south pole.

“We knew from the Apollo seismic experiment, which was four seismometers operated over a period of about seven years, that these were shallow lunar earthquakes, but we didn’t really know what the source was,” Waters said. “We also knew that the largest of the shallow lunar earthquakes detected by the Apollo seismometers was located near the south pole. It became a detective story to try to figure out what the source was, and it turned out That these were flawed young people, they are the best suspects.”

The most powerful earthquake on record was equivalent to a magnitude of 5.0. On Earth, this would be considered moderate, Waters said, but the moon’s lower gravity would make it feel worse.

“On Earth, you have very strong gravity that keeps you stuck to the surface,” he said. “On the Moon, it’s much smaller, so even the slightest acceleration of the ground if you’re walking will potentially throw you off balance.” ” “Such shocks can actually cause things to move around in low-gravity environments.”

Lunar earthquake: short-term vs. long-term effects

According to study co-author and NASA planetary scientist Renee Weber, the study’s findings will not impact the Artemis III landing zone selection process, and this is due to the scope and duration of the mission.

“This is because it is difficult to accurately predict how often moonquakes occur in a specific area, and like earthquakes, we cannot predict moonquakes,” Weber said. “Intense, shallow lunar earthquakes are rare and pose little risk to short-duration missions to the lunar surface.”

He said NASA has identified 13 candidate areas for landing Artemis III near the moon’s south pole, based on factors such as the ability to land safely in the area, the ability to meet scientific objectives, the availability of a launch window, and conditions. criteria have been used. 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 may actually take into account geographic features such as proximity to tectonic features and terrain.

“Moon Lantern”

Moonquakes could indeed be a problem for future human 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 Apollo seismic stations. .

However, Nakamura, who was not involved in the study, disagrees with the cause of the earthquake and said that Apollo data show that the events originate tens of kilometers below the surface.

“We still don’t know what causes shallow lunar earthquakes, but it’s not strike-slip faults 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 posed to astronauts by lunar earthquakes will be limited by the fact that, at least in the near future, humans will remain on the Moon for short periods of time, a few days at most. Husker, a research professor of geophysics at the California Institute of Technology, was also not involved in the study, according to Allen.

“It’s very unlikely that any major earthquakes will occur while they are there. However, it is good to know that these seismic sources (which cause earthquakes) exist. They could be an opportunity to better study the Moon as That’s what we do with earthquakes on Earth,” Husker said. “Until there is an actual lunar base, we need to have a better idea of ​​the actual seismic hazard of upcoming missions.”

That sentiment is shared by Jeffrey Andrews-Hanna, an associate professor of planetary science at the University of Arizona, who was not involved in the work. “Moonquake is an incredible tool for doing science,” he said in an email. “They are like lanterns in the Moon’s interior that illuminate its structure for us to see. Studying earthquakes at the south pole will tell us more about the Moon’s interior structure as well as its current activity. “