# Astronomers Quantify the Moon's Gradual Contraction and Seismic Risks New research reveals the moon's cooling process causes widespread, unpredictable lunar seismic activity. - **Source:** [Popular Science](https://www.popsci.com) - **Published:** 2026-10-14 - **Topic:** [Business](https://brifing.si/c/business) - **Original article:** - **On Brifing:** https://brifing.si/s/4b010445-baec-49dc-8203-44d8dc713978 ## Quantifying Lunar Contraction Rates Planetary geologist Thomas Watters led a study published in The Planetary Science Journal detailing the moon's shrinkage. Data from NASA’s Lunar Reconnaissance Orbiter Camera indicates the lunar radius has decreased by nearly 148 feet over the last 400 to 800 million years. This cooling process continues at a glacial, incremental pace. ## Annual Rate of Shrinkage The contraction occurs at a rate of approximately 2.4 to 4.3 inches per million years. On an annual basis, this shift measures just 0.1 micrometers. While these figures appear negligible, the cumulative effect over millions of years has fundamentally altered the lunar landscape, creating visible geological faults across the entire surface. ## Unique Seismic Plate Mechanics Earth experiences 90 percent of seismic activity near lithospheric plate boundaries. Conversely, the moon is encased in a single, shell-like plate. This structural difference means interior cooling generates slips and faults anywhere on the lunar surface. Consequently, moonquakes can occur at any location, rather than being restricted to specific tectonic fault lines. ## Mapping Ten Thousand Faults Researchers analyzed millions of images captured by the Lunar Reconnaissance Orbiter Camera over 17 years. This extensive review identified over 10,000 visible lunar faults. Thomas Watters noted that the volume of these young faults significantly exceeded initial expectations, confirming that the moon remains geologically active as its interior continues to cool down. ## Regional Stability and Crust Thickness Not all lunar regions exhibit the same level of seismic risk. Areas characterized by the thickest crust appear to possess fewer faults, suggesting higher relative stability. In contrast, thinner sections of the lunar crust are more prone to faulting, providing a clearer map for identifying potentially hazardous zones for future exploration missions. ## Implications for Future Exploration Understanding the distribution and frequency of moonquakes is critical for long-term human presence on the moon. NASA utilizes this data to plan infrastructure and mission safety. By identifying stable regions versus active fault zones, space agencies can better mitigate risks associated with seismic activity during extended lunar surface operations and habitation. ## Ongoing Geological Evolution The moon is not a static celestial body but one undergoing constant internal change. As the interior continues to lose heat, the growth of existing faults and the formation of new ones are expected to persist. This ongoing contraction ensures that the lunar surface remains dynamic, requiring continuous monitoring through advanced orbital instrumentation. ## Scientific Significance of Findings This research provides essential insights into lunar history and current geological behavior. By quantifying the contraction rate and mapping fault distribution, scientists have established a baseline for lunar seismicity. These findings bridge the gap between historical planetary cooling models and the practical requirements for establishing a sustainable human presence on the moon. ## Sources covering this story - https://www.popsci.com/science/how-fast-is-the-moon-shrinking/ — --- _Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._