Scientists discover moon is shrinking, causing landslides and instability at lunar south pole

Earth’s moon has shrunk by more than 150 feet in circumference as its core gradually cooled over the past several hundred million years. Just as a grape wrinkles when it shrinks to a raisin, the moon also develops wrinkles when it shrinks. But unlike the flexible skin of a grape, the moon’s surface is fragile, causing faults to form where sections of crust push against each other.

A team of scientists has discovered evidence that this continued shrinking of the Moon has led to notable surface deformation in its south polar region, including areas proposed by NASA for crewed Artemis III landings. Since faulting caused by the shrinking moon is often accompanied by seismic activity such as moonquakes, locations near or within these fault zones could pose hazards to future human exploration efforts.

In an article published in The Journal of Planetary Science, the team linked a group of faults located in the Moon’s south polar region to one of the most powerful earthquakes recorded by Apollo seismometers more than 50 years ago. Using models to simulate the stability of surface slopes in the region, the team found that certain areas were particularly vulnerable to landslides from earthquake shaking.

“Our modeling suggests that shallow moonquakes capable of producing strong ground shaking in the south polar region are possible from slip events on existing faults or the formation of new thrust faults,” said The study’s lead author, Thomas R. Watters, senior scientist emeritus of the Center for Earth and Planetary Studies at the National Air and Space Museum.

“The global distribution of young thrust faults, their potential for activity, and the possibility of forming new thrust faults from ongoing global contraction should be considered when planning the location and stability of permanent outposts on the Moon.”

Shallow moonquakes occur near the moon’s surface, only about a hundred kilometers deep in the crust. Similar to earthquakes, shallow earthquakes are caused by faults within the Moon and can be powerful enough to damage buildings, equipment, and other man-made structures.

But unlike earthquakes, which tend to last only seconds or minutes, shallow moonquakes can last for hours or even an entire afternoon, like the magnitude 5 moonquake recorded by the network Apollo passive seismic network in the 1970s, which the research team connected to a passive seismic network. group of faults detected more recently by the Lunar Reconnaissance Orbiter.

According to Nicholas Schmerr, co-author of the paper and associate professor of geology at the University of Maryland, this means that shallow moonquakes can devastate hypothetical human settlements on the Moon.

“You can think of the surface of the Moon as being dry, crushed gravel and dust. For billions of years the surface has been hit by asteroids and comets, the resulting angular fragments are constantly ejected during impacts,” Schmerr explained.

“As a result, the reworked surface material can be micron-sized to boulder-sized, but all very poorly consolidated. Loose sediments make shaking and landslides very possible.”

Researchers continue to map the Moon and its seismic activity, hoping to identify more places that might be dangerous for human exploration. NASA’s Artemis missions, scheduled to launch their first crewed flight in late 2024, hope to eventually establish a long-term presence on the Moon and eventually learn to live and work on another world through observatories, outposts and colonies based on the Moon.

“As we move closer to the crewed Artemis mission launch date, it is important to keep our astronauts, equipment and infrastructure as safe as possible,” Schmerr said.

“This work helps us prepare for what awaits us on the Moon, whether that’s engineering structures that can better withstand lunar seismic activity or protect people from truly dangerous areas.”