When you look at the night sky, you might not realize it.
But our moon is actually shrinking – and that could be disastrous for NASA.
The moon is shrinking as its dense, metallic core gradually cools, according to a new study.
As a result, the moon’s surface contracts and becomes more brittle – and in turn more susceptible to seismic tremors known as ‘moonquakes’.
If these tremors cause landslides, they could pose a danger to NASA’s Artemis astronauts after they eventually land on the moon, scientists at the University of Maryland warn.
Earth’s moon shrank in circumference by more than 50 meters as its core gradually cooled over the past few hundred million years. Pictured is the southern part of the moon, with blue boxes indicating the proposed locations of the upcoming Artemis III moon landing. Magenta dots indicate possible epicenters of a very strong moonquake in the early 1970s
According to the team of experts, the moon has been shrinking very gradually in the 4.4 billion years since its formation.
Its circumference has shrunk by more than 50 meters as its core has cooled over the past hundred million years.
In much the same way that a grape wrinkles as it shrinks into a raisin, the moon also develops wrinkles as it shrinks.
But unlike the flexible skin of a grape, the moon’s surface is brittle, causing fractures to form where parts of the crust push against each other.
This causes the moonquakes – and can lead to landslides that endanger lunar residents.
“As we get closer to the launch date of the crewed Artemis mission, it is important to keep our astronauts, our equipment and infrastructure as safe as possible,” said study author Nicholas Schmerr, a geologist at the University of Maryland.
“This work helps us prepare for what awaits us on the moon – whether it’s engineering structures that can better withstand lunar seismic activity or protecting people from truly dangerous zones.”
For their research, the scientists linked a group of faults in the moon’s south polar region to one of the most powerful moonquakes recorded by Apollo seismometers on March 13, 1973, called the N9 event.
Using models to simulate the stability of surface slopes in the region, the team found that some areas were particularly vulnerable to landslides due to seismic tremors.
Scientists say moonquakes have happened before and could happen again. Here, arrows point to ‘scarps’ – long structures interpreted as tectonic in nature and the result of a thrust fault – at the moon’s south pole
Pictured: Part of the inner wall and floor of Shackleton Crater at the moon’s south pole. Boulder falls (white arrows) suggest that recent seismic shaking events have occurred in the crater
Space agencies are generally interested in landing on the southern part of the moon (pictured) because of the rich reserves of water ice there
The experts say the moon’s continued shrinkage has led to notable surface warping in the south polar region.
Coincidentally, the south of the moon is where the Artemis III mission – the first mission to put humans on the moon in more than 50 years – plans to land.
Later in the Artemis program, probably after 2030, NASA plans to establish a base camp in the southern lunar region.
Space agencies are generally interested in landing on the moon’s southern portion because of the rich reserves of water ice there.
It could provide a source of drinking water for lunar researchers and help cool equipment, or break down to produce hydrogen for fuel and oxygen for breathing.
But moonquakes and resulting landslides have the potential to destroy the Artemis base camp, including buildings and infrastructure.
The study authors are concerned about shallow moonquakes (SMQs), which occur near the moon’s surface, only about a hundred kilometers deep in the crust.
Artemis Base Camp: NASA plans to establish a base camp in the southern lunar region by the end of this decade (artist’s impression)
Artemis is the successor to NASA’s Apollo program from the 1960s and 1970s. In this famous NASA photo, astronaut Buzz Aldrin Jr. poses. for a photo next to the American flag on the moon during the Apollo 11 mission on July 20, 1969
Like earthquakes on Earth, they can be strong enough to damage buildings, equipment and other man-made structures.
But unlike earthquakes, which usually last only a few seconds or minutes, shallow moonquakes can last hours and even an entire afternoon.
The researchers will continue to map the moon and its seismic activity, hoping to identify more locations that could be dangerous to human exploration.
Although the next moon landing was recently pushed back to 2026, this is still relatively soon, especially considering we’re still learning about our lunar neighbor.
“Mild seismic shaking may be all that is needed to trigger regolith landslides,” the team warns in their paper, published in The Planetary Science Journal.
‘The potential for strong seismic events due to active thrust faults must be considered when preparing and locating permanent outposts and poses a potential hazard to future robotic and human exploration of the Antarctic.’