Cooling Interior Causes Moon to Shrink
Earth’s natural satellite, the Moon, is slowly shrinking as its interior cools, a geological process that triggers moonquakes and landslides across the lunar surface. A study published in The Planetary Science Journal on October 14, 2026, and reported by detikcom, reveals that the lunar radius has decreased by roughly 42 to 46 meters over the past 400 million years.
Mapping Lunar Faults with NASA Data
Researchers from the Smithsonian and NASA identified the phenomenon by analyzing thousands of small cliffs and ridges across the lunar surface. Using satellite imagery from the Lunar Reconnaissance Orbiter (LRO), scientists mapped more than 10,000 individual faults. Out of that total, 5,470 faults measure longer than one kilometer. These dimensions allowed researchers to calculate crustal displacement rates and total radius reduction.
The number of young thrust faults mapped in the LROC images was much greater than I ever expected,
said Thomas Watters, the study’s lead author from the Smithsonian National Air and Space Museum. Watters noted that as the interior cools and contracts, the growth of existing faults and the formation of new ones continues today.
Brittle Crust Triggers Shallow Moonquakes
Unlike the elastic skin of a drying grape, the Moon’s rocky crust is stiff and brittle. As the interior cools, the crust breaks and shifts, creating steep scarps known as thrust faults. Data indicates that areas with thicker crusts show fewer faults, linking crustal thickness directly to surface stability. This ongoing contraction generates significant seismic activity, which researchers tied directly to shallow moonquakes recorded by Apollo mission instruments during the 1970s.
Stresses released during these moonquakes reach approximately 4 megapascal (MPa), equivalent to 40 times Earth’s atmospheric pressure. An analysis of 28 specific moonquake epicenters showed that 13 occurred within a 90-kilometer radius of active fault scarps. Subsequent comparisons of orbital imagery confirmed fresh rockfalls and landslides surrounding these fault zones.
Evaluating Future Landing Sites
NASA uses these fault maps to assess geological hazards for upcoming crewed missions and future permanent lunar bases. Understanding where active seismic zones and landslide risks cluster helps mission planners select safe landing locations that avoid areas vulnerable to tectonic movement.
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