# Astronomers Quantify the Moon's Gradual Contraction and Seismic Risks New research reveals the moon's shrinking rate and its impact on lunar seismic activity. - **Source:** [Popular Science](https://brifing.si/source/cc3d313a-759c-4802-b881-fc8585f35ef9) - **Published:** 2026-10-14 - **Topic:** [Business](https://brifing.si/c/business) - **Original article:** - **On Brifing:** https://brifing.si/s/535f474e-f717-4709-b740-bca6f399a16a ## Quantifying Lunar Contraction Rates Planetary geologist Thomas Watters led a study published in The Planetary Science Journal detailing lunar shrinkage. Using data from NASA’s Lunar Reconnaissance Orbiter Camera, researchers calculated that the moon’s radius has decreased by nearly 148 feet over the last 400 to 800 million years. This cooling process continues at a glacial pace today. ## Annual Contraction Measurements The moon's contraction rate is estimated at approximately 2.4 to 4.3 inches per million years. On an annual basis, this equates to a mere 0.1 micrometer of shrinkage. Despite the extremely slow speed of this physical change, the cumulative effect over millions of years has significantly altered the moon's geological landscape and stability. ## Seismic Activity Mechanisms Unlike Earth, where 90 percent of seismic activity occurs at lithospheric plate boundaries, the moon is encased in a single, shell-like plate. This unique structure means that interior cooling can generate slips and faults anywhere on the lunar surface. Consequently, moonquakes can occur at any location without the predictability found on Earth. ## Mapping Lunar Fault Lines Researchers analyzed millions of images captured by the Lunar Reconnaissance Orbiter Camera over a 17-year period. This extensive visual survey allowed the team to identify and tally over 10,000 visible lunar faults. The sheer number of these young faults suggests that the moon remains geologically active as its interior continues to cool down. ## Regional Stability Variations Not all lunar regions exhibit the same level of seismic vulnerability. Areas characterized by the thickest crust appear to have fewer faults, suggesting higher levels of geological stability compared to thinner sections. These findings provide a clearer understanding of which lunar zones might be safer for future exploration or long-term infrastructure development projects. ## Future Fault Formation Thomas Watters noted that the number of young faults revealed in the LROC images exceeded initial expectations. As the moon’s interior continues its long-term cooling and contraction, experts anticipate the growth of existing faults. Furthermore, the ongoing process will likely lead to the formation of entirely new faults across the lunar surface. ## Strategic Planning for Exploration Understanding the frequency and distribution of moonquakes is essential for NASA's future mission planning. By identifying stable regions versus high-risk fault zones, space agencies can better determine optimal locations for human habitats. This geological data serves as a critical foundation for ensuring the safety of a long-term human presence on the moon. ## Scientific Implications of Findings This research bridges the gap between historical lunar cooling and current seismic risks. By quantifying the contraction rate, scientists have gained a vital tool for predicting future geological events. These insights are not merely academic; they are practical requirements for any organization planning to establish permanent operations on the lunar surface. ## 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._