The Moon Is Shrinking (And Getting Moonquakes)

Picture this. You’re standing inside a habitat on the Moon’s south pole. The ground begins to tremble. On Earth, you’d brace yourself for a few seconds and it would pass. Here, the shaking doesn’t stop. It goes on for ten minutes. The whole Moon is ringing like a bell, and there’s nothing you can do but wait.

That scenario isn’t science fiction. It’s what the Apollo seismometers recorded. And new research published in February 2026 suggests the Moon’s surface is more geologically restless than we thought, particularly in the exact regions where we’re planning to send astronauts next.

A new map of a shrinking world

Planetary scientists have just published the first complete global map of features called small mare ridges: subtle wrinkles that run across the Moon’s broad, dark plains. They found 1,114 that nobody had catalogued before, bringing the total to 2,634. These ridges average about 124 million years old. On a 4.5-billion-year-old Moon, that’s essentially yesterday.

The ridges exist because the Moon is shrinking. When it formed (most likely from debris created when a Mars-sized object crashed into the young Earth), it was extremely hot. Over billions of years, its interior has been cooling. As it cools, it contracts. The problem is that the Moon doesn’t have tectonic plates like Earth. Our planet’s crust is broken into large moving pieces that slide and flex to manage stress. The Moon’s crust is one solid shell. When the interior shrinks, the shell can’t flex. It cracks. Sections of rock get pushed up and over each other. Over hundreds of millions of years, the Moon has lost about 50 metres of diameter.

Fifty metres doesn’t sound like much for a world 3,474 kilometres across. But the cracking it produces is very real.

Moonquakes: real, and strange

The Apollo astronauts left seismometers on the lunar surface in the late 1960s and early 1970s. Those instruments recorded something unexpected: the Moon has quakes. Shallow moonquakes can reach about 5.0 on the Richter scale, roughly a moderate earthquake. But here’s the difference. On Earth, a magnitude 5 quake lasts seconds. On the Moon, because the rock is dry and fractured and there’s no water to dampen vibrations, a moonquake can ring on for over ten minutes. The whole body vibrates. It’s deeply counterintuitive: a world with no atmosphere, no liquid water, no obvious signs of activity, shaking for ten minutes at a stretch.

In December 2025, a separate study confirmed that moonquakes were the main force behind shifting terrain at the Apollo 17 landing site. And the most powerful shallow moonquake ever recorded had its epicentre near the lunar south pole.

The south pole problem

This matters because NASA’s Artemis programme is aiming to land astronauts at the south pole. Permanently shadowed craters there may contain water ice: potential drinking water, breathable oxygen, even rocket fuel. It’s the most promising site for a long-term human presence. But the new mapping shows these areas are laced with young faults. Where there are young faults, there are potential moonquakes. Some steep crater walls where astronauts might explore could be vulnerable to landslides from even moderate shaking.

Engineers are already responding. A new instrument called the Farside Seismic Suite is planned for 2026 to expand our understanding of lunar seismic activity. And structural guidelines for future habitats are being drafted with earthquake-resistant principles borrowed from Tokyo and San Francisco. We’re applying lessons learned from living on one restless world to the challenge of living on another.

Talking about this with your kids

The Moon is shrinking. That’s a great opener at dinner. Ask them why (it’s cooling down, like how a cake gets slightly smaller as it cools after baking). Then try this: set a timer for ten minutes and ask everyone to sit completely still for the full duration. That’s how long a moonquake lasts. It feels like forever. Now ask: if you were building a house on the Moon, what would you need to worry about? The answer isn’t just radiation and vacuum. It’s the ground moving under your feet.

We spent decades thinking of the Moon as geologically dead. It’s not. It’s still changing, still cracking. And if we’re going to live there, we need to build for a world that hasn’t finished settling.

Sources and further reading

Study in Planetary Science Journal, February 2026: https://iopscience.iop.org/journal/PSJ

ScienceDaily coverage: https://www.sciencedaily.com/releases/2026/02/260218031532.htm

NASA: Moonquakes overview: https://science.nasa.gov/moon/moonquakes

NASA: Shrinking Moon and Artemis: https://www.nasa.gov/solar-system/moon/shrinking-moon-causing-moonquakes

Apollo 17 study, December 2025: https://www.sciencedaily.com/releases/2025/12/251205054743.htm