Wacky WorldSpace
Short answer: The Moon experiences moonquakes. Apollo astronauts installed seismometers that recorded vibrations from deep tidal stresses, shallow tectonic events, meteoroid impacts and the expansion and contraction caused by extreme temperature changes.
How were moonquakes discovered?
The Apollo programme did more than collect rocks. Astronauts deployed scientific packages on the lunar surface, including seismometers. A network of four stations operated from the Apollo era until 1977, sending years of data back to Earth. The instruments detected signals that scientists could separate by their depth, shape, timing and relationship to impacts.
What causes the Moon to shake?
There is not one single cause. Deep moonquakes occur hundreds of kilometres below the surface and repeat in patterns connected with Earth’s gravitational pull. That tidal force continually flexes the Moon. Shallower events appear to be tectonic: the Moon has cooled over billions of years, contracted and developed thrust faults as its brittle crust adjusted.
Meteoroids also strike the airless lunar surface and send vibrations through the ground. In addition, rocks near the surface expand in intense daytime heat and contract during the freezing lunar night. This thermal cycling can create small, very shallow seismic events.
How are moonquakes different from earthquakes?
Earthquakes are often driven by moving tectonic plates, while the Moon has no Earth-like system of active plate tectonics. Lunar rock is also much drier and more fractured. NASA notes that some moonquake vibrations can continue for more than ten minutes because seismic energy is scattered and loses energy differently inside the Moon.
Is the Moon still shrinking?
Images from NASA’s Lunar Reconnaissance Orbiter show thousands of small thrust-fault scarps. These cliff-like features indicate that the crust has been compressed as the Moon cooled. NASA estimates that the lunar diameter has become about 50 metres smaller over the last several hundred million years, and some faults may still be active.
Why moonquakes matter for future bases
Engineers need to know how often strong shaking occurs and where faults lie before building long-lived habitats, landing pads or observatories. Apollo’s instruments covered only a limited area on the near side, so future seismic stations—especially on the far side—can reveal a much fuller picture of lunar activity and internal structure.
Four useful categories
- Deep: connected with tidal flexing.
- Shallow: likely tectonic and potentially stronger.
- Impact: caused by natural or planned objects striking the surface.
- Thermal: caused by rapid heating and cooling of surface rock.
Evidence and limits
“Moonquake” is a convenient broad name, not proof that lunar geology works exactly like Earth’s. Apollo locations and instruments limited the precision of some estimates, and researchers continue reanalysing the old recordings with modern methods. New measurements are necessary to map hazards reliably across the whole Moon.
Sources
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