What Really Caused Apollo 17's Moon Landslides?

For decades, scientists assumed that boulder falls and landslides near the Apollo 17 landing site were caused by meteoroid impacts. It was a reasonable guess. The Moon has no atmosphere to burn up incoming space rocks, so impacts are common. But new research has overturned that assumption. Repeated moonquakes along an active fault line, not meteor strikes, are the real cause of shifting terrain in the Taurus-Littrow valley.

This discovery changes how we view the Moon. It is not a geologically dead world frozen in time. Instead, it still experiences internal tectonic activity billions of years after its formation. For future astronauts planning long-term stays, understanding these moonquakes is as important as knowing where to find water ice, which we covered in our article on where to find water ice on the Moon's south pole.

What Is the Lee-Lincoln Fault?

The Lee-Lincoln fault is a thrust fault located directly within the Apollo 17 landing area in the Taurus-Littrow valley. A thrust fault forms when one section of crust is pushed up and over another due to compressional forces. On Earth, such faults are associated with earthquakes. On the Moon, they produce moonquakes.

According to NASA's analysis combining Apollo samples with Lunar Reconnaissance Orbiter data, the Lee-Lincoln fault has been the source of multiple strong shallow moonquakes. These quakes generated enough ground acceleration to trigger landslides and dislodge boulders from both the North and South massifs surrounding the valley. The evidence comes from matching boulder track patterns with fault movement rather than impact cratering signatures.

How Moonquakes Differ from Earthquakes

Moonquakes are not simply smaller versions of earthquakes. They behave differently because the Moon lacks water in its interior and has a much drier, more rigid crust. While earthquakes typically last seconds to minutes, moonquakes can reverberate for hours due to the absence of damping materials like groundwater.

There are four types of moonquakes: deep tidal quakes caused by Earth's gravitational pull, thermal quakes from surface expansion and contraction, meteoroid-induced quakes, and shallow tectonic quakes like those at Lee-Lincoln. The shallow tectonic quakes are the most relevant for human exploration because they occur near the surface and can be strong enough to damage structures. Unlike Earth, where plate tectonics drive most seismic activity, lunar quakes result from global contraction as the Moon slowly cools and tidal stresses from Earth's gravity.

This distinction matters when comparing planetary behavior. Just as understanding how fast Earth spins helps explain our planet's magnetic field and day-night cycle, understanding lunar tidal forces explains why the Moon still shakes despite having no plates or volcanoes.

Why This Matters for Future Lunar Bases

Knowing that the Moon is seismically active affects where and how we build. If future habitats are placed near active faults like Lee-Lincoln, they could face repeated shaking over decades. According to detailed coverage by Watchers.news, researchers have now developed methods to estimate moonquake frequency along specific faults using LRO imagery and Apollo-era samples. This allows mission planners to create seismic hazard maps similar to those used on Earth.

The good news is that moonquakes are generally weaker than major earthquakes. The bad news is their longevity and unpredictability. A habitat designed for Mars or Earth conditions might fail under prolonged lunar vibration. Engineering solutions will need to account for hours-long resonance, not just peak ground acceleration.

Key Takeaways

• Landslides at Apollo 17's Taurus-Littrow site were caused by moonquakes on the Lee-Lincoln fault, not meteoroid impacts.
• The Lee-Lincoln fault is an active thrust fault producing shallow tectonic moonquakes capable of triggering boulder falls.
• Moonquakes differ from earthquakes by lasting hours due to the Moon's dry, rigid interior lacking seismic damping.
• Shallow tectonic moonquakes pose engineering challenges for future lunar bases requiring specialized vibration-resistant design.
• Seismic hazard mapping using LRO and Apollo data now enables safer site selection for Artemis-era infrastructure.

The Moon is quieter than Earth, but it is not silent. Recognizing its subtle internal rhythms ensures that when humans return to stay, we build wisely. The lessons from Apollo 17's boulder-strewn valley remind us that even familiar worlds still hold surprises beneath their surfaces.