Earth’s moon is shrinking. Here’s what scientists say that could mean

Jan 31, 2024, 5:01 PM

A new study says as the moon’s core cools and shrinks, its surface develops creases that create “moonquakes” and landslides, and seen here is a composite image of the moon with data from 1994. Mandatory Credit: NASA

(CNN) — A region of the moon that’s at the center of a new international space race because it may contain water ice could be less hospitable than once thought, new research has found.

Interest in the lunar south pole spiked last year, when India’s Chandrayaan-3 mission made the first successful soft landing in the area, just days after Russia’s Luna-25 spacecraft crashed en route to attempt the same feat. NASA has selected the region as the landing site for its Artemis III mission, which could mark the return of astronauts to the moon as soon as 2026, and China also has plans to create future habitats there.

But now a study funded by NASA is ringing an alarm bell: As the moon’s core gradually cools and shrinks, its surface develops creases — like a grape shriveling into a raisin — that create “moonquakes” that can last for hours, as well as landslides. Much like the rest of the natural satellite’s surface, the area of the south pole that is the subject of so much interest is prone to these seismic phenomena, potentially posing a threat to future human settlers and equipment.

“This is not to alarm anyone and certainly not to discourage exploration of that part of the south pole of the moon,” said the study’s lead author, Thomas R. Watters, a senior scientist emeritus in the National Air and Space Museum’s Center for Earth and Planetary Studies, “but to raise the caution that the moon is not this benign place where nothing is happening.”

Finding the source of moonquakes

The moon has shrunk by about 150 feet in circumference over the last few million years — a significant number in geological terms but too small to cause any ripple effect on Earth or to tidal cycles, according to researchers.

On the lunar surface, however, it’s a different story. Despite what its appearance might suggest, the moon still has a hot interior, which makes it seismically active.

“There is an outer core that’s molten and is cooling off,” Watters said. “As it cools, the moon shrinks, the interior volume changes and the crust has to adjust to that change — it’s a global contraction, to which tidal forces on the Earth also contribute.”

Because the moon’s surface is brittle, this pulling generates cracks, which geologists call faults. “The moon is thought of as being this geologically dead object where nothing has happened for billions of years, but that couldn’t be more far from the truth,” Watters said. “These faults are very young and things are happening. We’ve actually detected landslides that have occurred during the time that the Lunar Reconnaissance Orbiter has been in orbit around the moon.”

NASA’s Lunar Reconnaissance Orbiter, or LRO, launched in 2009, and it’s mapping the moon’s surface with various instruments. In the new study, published January 25 in The Planetary Science Journal, Watters and his colleagues used data collected by LRO to link a powerful moonquake — detected with instruments left by Apollo astronauts more than 50 years ago — to a series of faults in the lunar south pole.

“We knew from the Apollo seismic experiment, which were four seismometers that operated for 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 kind of became a sort of a detective story to try to figure out what the source was, and it turns out that these young faults are the best suspect.”

The strongest recorded quake was the equivalent of magnitude 5.0. On Earth, that would be considered moderate, but the moon’s lower gravity would make it feel worse, Watters said.

“On the Earth, you have a much stronger gravity keeping you attached to the surface. On the moon, it’s much smaller, so even a little bit of ground acceleration is going to potentially pop you off your feet, if you’re walking along,” he said. “That kind of shaking can really start throwing things around in a low G environment.”

Moonquakes: Short-term vs. long-term implications

The findings of the study will not affect the Artemis III landing region selection process, and that’s due to the scope and duration of the mission, according to study coauthor and NASA planetary scientist Renee Weber.

“This is because estimating how often a specific region experiences a moonquake is difficult to do accurately, and like earthquakes, we can’t predict moonquakes,” Weber said. “Strong shallow moonquakes are infrequent and pose a low risk to short-term missions on the lunar surface.”

NASA has identified 13 Artemis III candidate landing regions near the lunar south pole, she added, using criteria such as the ability to land safely in the region, the potential to meet science objectives, launch window availability and conditions such as 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 indeed factor in geographic characteristics such as proximity to tectonic features and terrain.

Like flashlights in the moon

Moonquakes could indeed be a problem for future manned landing missions, said Yosio Nakamura, a 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 with the study, disagrees about the cause of the quakes, 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 is not the sliding fault near the surface,” he said. “Regardless of what causes those quakes, it is true that they pose a potential threat to future landing missions, and we need more data about them.”

Regardless of the underlying cause, the potential danger 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 with the study.

“It is very unlikely that a large moonquake will happen while they are there. However, it is good to know that these seismic sources (causing the quakes) exist. They can be an opportunity to better study the moon as we do on the Earth with earthquakes,” Husker said. “By the time there is an actual moon base, we should have a much better idea of the actual seismic hazard with upcoming missions.”

That sentiment is shared by Jeffrey Andrews-Hanna, an associate professor of planetary science at the University of Arizona, who also didn’t participate in the work. “Moonquakes are an incredible tool for doing science,” he said in an email. “They are like flashlights in the lunar interior that illuminate its structure for us to see. Studying moonquakes at the south pole will tell us more about the Moon’s interior structure as well as its present-day activity.”

The-CNN-Wire™ & © 2024 Cable News Network, Inc., a Warner Bros. Discovery Company. All rights reserved.

KSL 5 TV Live


A local organization is keeping kids away from crime and drugs one bike at a time. (KDRV via CNN Ne...

Rocky Walker, CNN

Familia Unida: Keeping kids away from drugs and crime by teaching them to work with their hands

A local organization is keeping kids away from crime and drugs one bike at a time. Familia Unida is a nonprofit that teaches children to channel aggression and negative experiences into healthy and constructive life skills through activities such as bike and car building.

6 hours ago

The US Centers for Disease Control and Prevention issued an official health advisory warning about ...

Jacqueline Howard, CNN

CDC warns access to ADHD meds may be disrupted after arrests of health-care startup executives

People taking medications for ADHD, or attention-deficit hyperactivity disorder, may face disruptions in accessing treatment after the arrests of two health-care startup executives that distributed such drugs to adults across the United States.

7 hours ago

The family said the doctors told them she may have experienced what is known as a cryptic pregnancy...

Mike Bergazzi , Jon Burkett

Unaware she was pregnant, this mom gave birth at Taco Bell: ‘A miracle, out of nowhere’

A woman was shocked when she went into labor at Taco Bell. She didn't know she was pregnant.

14 hours ago

Emergency vehicles surround the hijacked bus after a harrowing chase through two Atlanta-area count...

Shawn Nottingham, Nick Valencia and Elizabeth Wolfe, CNN

Bus passengers frantically texted loved ones as gunman hijacked an Atlanta commuter bus

A gunman had hijacked a commuter bus with 17 people inside and shot one of them with the passenger’s own gun, authorities said.

2 days ago

Coast Guard Commandant Adm. Linda Fagan testified in front of senators Tuesday. (Andrew Harnik/Gett...

Blake Ellis, Melanie Hicken and Audrey Ash, CNN

‘A deep moral rot’: Coast Guard leader grilled by senators at hearing on sexual assault cover-up

Senators leveled accusations at the U.S. Coast Guard Commandant Adm. Linda Fagan on Tuesday, alleging that she fostered a "culture of concealment."

2 days ago

A pro-Palestinian demonstrator is taken into custody Monday outside Dodd Hall at UCLA.
(Etienne Lau...

Jillian Sykes, Holly Yan and Taylor Romine, CNN

27 protesters arrested after pro-Palestinian encampments formed on UCLA campus, university says

A total of 27 people were arrested after setting up multiple pro-Palestinian encampments on UCLA’s campus Monday that police said were unlawful, according to a statement from UCLA leadership.

2 days ago

Sponsored Articles

Photo courtesy of Artists of Ballet West...

Ballet West

The rising demand for ballet tickets: why they’re harder to get

Ballet West’s box office is experiencing demand they’ve never seen before, leaving many interested patrons unable to secure tickets they want.

Electrician repairing ceiling fan with lamps indoors...

Lighting Design

Stay cool this summer with ceiling fans

When used correctly, ceiling fans help circulate cool and warm air. They can also help you save on utilities.

Side view at diverse group of children sitting in row at school classroom and using laptops...

PC Laptops

5 internet safety tips for kids

Read these tips about internet safety for kids so that your children can use this tool for learning and discovery in positive ways.

Women hold card for scanning key card to access Photocopier Security system concept...

Les Olson

Why printer security should be top of mind for your business

Connected printers have vulnerable endpoints that are an easy target for cyber thieves. Protect your business with these tips.

Modern chandelier hanging from a white slanted ceiling with windows in the backgruond...

Lighting Design

Light up your home with these top lighting trends for 2024

Check out the latest lighting design trends for 2024 and tips on how you can incorporate them into your home.

Technician woman fixing hardware of desktop computer. Close up....

PC Laptops

Tips for hassle-free computer repairs

Experiencing a glitch in your computer can be frustrating, but with these tips you can have your computer repaired without the stress.

Earth’s moon is shrinking. Here’s what scientists say that could mean