Moonquakes, while generally weaker than Earth’s earthquakes, could present risks to future bases, habitats, and equipment. Photo credit: MUSTAFA YANAR/Shutterstock
Scientists studying Earth’s only natural satellite have discovered compelling evidence that the Moon is not a static world but is still slowly shrinking, with implications for future lunar exploration and seismic activity. The findings come from a detailed global analysis of subtle geological features across the lunar surface, revealing that the Moon’s interior continues to cool and contract, creating stresses that could cause moonquakes.
New Map Reveals Widespread Lunar Faults
A team of planetary scientists from the Smithsonian’s National Air and Space Museum’s Center for Earth and Planetary Studies has produced the first comprehensive global map of small mare ridges (SMRs), subtle ridge-like formations across the Moon’s maria, the dark volcanic plains visible from Earth. These features are now understood to be tectonic in origin, formed when sections of the lunar crust are compressed due to overall contraction of the Moon’s interior.
These ridges are not isolated curiosities. The researchers catalogued 1,114 newly identified SMRs on the near side of the Moon, bringing the known total to 2,634 segments. Analysis shows that these ridges are geologically young, averaging around 124 million years old, which in geological terms means they are among the most recent landforms on the lunar surface.
Lead author Cole Nypaver, a post-doctoral geologist on the team, says this new catalog offers a globally complete perspective on recent lunar tectonism, a major step forward in understanding how the Moon continues to evolve.
Why the Moon Keeps Shrinking
The Moon formed about 4.5 billion years ago and was once molten. Over billions of years, it has gradually cooled. Unlike Earth, which releases internal heat through active plate tectonics and volcanism, the Moon’s interior has largely solidified, leaving a rigid outer crust. As this interior cools further today, the entire lunar body contracts slightly, a process somewhat akin to how a ripe grape wrinkles when it dries into a raisin.
This contraction generates compressional stress within the crust. Because the lunar crust does not have moving plates like Earth, these stresses instead form thrust faults, places where one portion of crust is pushed up and over a neighbouring section. Lobate scarps, larger fault cliffs previously observed by NASA spacecraft, are one well-known example of such features. The SMRs revealed by the new study appear to form through similar processes but occur in the lunar maria rather than the highland regions.
Moonquakes: A Seismic Reality
The key significance of the new research lies in its implications for moonquakes. On Earth, earthquakes occur at the edges of moving tectonic plates. But on the Moon, quakes arise from internal stresses and the readjustment of faults created as the Moon continues to shrink. The discovery that SMRs form through the same compressional forces as the better-known lobate scarps means that researchers can now identify a far greater set of potential seismic sources across the lunar surface than previously recognised.
Previous studies have shown that lunar seismic activity is real, albeit generally weaker than typical terrestrial earthquakes, but some moonquakes can still be significant. Data from instruments left on the Moon by the Apollo missions in the 1970s recorded tremors that lasted up to ten minutes and reached magnitudes that would concern future lunar settlers.
This ongoing tectonic activity underscores that Earth’s closest celestial neighbour is not geologically dead, as once thought. Instead, its crust continues to adjust and evolve over long timescales.
Implications for Future Lunar Missions
The discovery of widespread SMRs has direct relevance for space agencies planning long-term lunar exploration and habitation. NASA’s Artemis programme, which aims to return astronauts to the Moon and establish a sustained human presence, highlights the importance of understanding lunar geology, especially when selecting landing sites and planning the construction of surface infrastructure.
Moonquakes could present risks to future bases, habitats, and equipment if they occur near volcanic plains or areas of concentrated faulting. By mapping the distribution of SMRs and related features, scientists can better predict where seismic stresses might be highest and help mission planners mitigate those risks.
A Changing Picture of the Moon
For decades, scientists believed the Moon to be a static, largely unchanging world. But the latest research paints a much more dynamic picture. The ongoing contraction of the lunar interior and the resulting tectonic adjustments show that the Moon is still evolving, albeit slowly.
Future missions carrying modern seismometers, rovers, and landers will help scientists further refine their understanding of lunar geology. For now, the discovery of thousands of young tectonic features adds a new chapter to our knowledge of Earth’s nearest neighbour, reminding us that even ancient celestial bodies can still surprise.
