For decades, scientists have considered the moon a dead world—a silent, unchanging landscape where nothing stirs. However, a new study has challenged this idea. For the first time, researchers have mapped and dated fresh boulder falls across the moon, showing that its surface is more active than previously imagined.
These boulders, ranging in size from several meters to hundreds of meters and weighing up to a few tons, occasionally tumble down cliffs and crater walls, leaving bright tracks of disturbed lunar dust behind.
“For a long time, there was this belief that the moon is geologically dead. Our study shows that boulders with sizes ranging (from) tens to hundreds of meters and (with) weights in tons have moved from their places over time,” Sivaprahasam Vijayan, lead researcher and an associate professor at the Physical Research Laboratory in Ahmedabad, India, told EOS.
This discovery not only changes our understanding of lunar geology but could also guide future missions to regions where the moon’s surface is still active.
Tracking the moon’s rolling stones
Finding recent boulder falls on the moon has been a long-standing challenge. Traditional studies had mapped boulder tracks but could not reliably tell which ones were new, because older tracks gradually fade due to space weathering.
The recent breakthrough came from looking for boulder fall ejecta (BFE), the fresh lunar material scooped up and deposited along a boulder’s path. These ejecta patterns appear brighter than the surrounding surface, forming streaks along the track that make it possible to distinguish new movements from old.
To identify these tracks, the researchers manually analyzed thousands of images of the moon’s surface between 40° north and 40° south latitude, where sunlight makes the bright trails visible. They then studied high-resolution images from NASA’s Lunar Reconnaissance Orbiter taken between 2009 and 2022 to confirm the movement and the presence of ejecta along the paths.
In total, they found 245 fresh boulder tracks covering around 373 kilometers. About 46 percent were on the moon’s Mare regions, and 54 percent in the Highlands, with 62 percent of locations hosting multiple tracks, suggesting these areas experience repeated boulder falls.
The team estimated the age of these tracks by comparing them with nearby craters whose ages are known from their ejecta blankets, a method long used in lunar studies. Many of these craters are around 400,000 years old, meaning the boulder tracks on their slopes are much younger.
Some tracks were also observed near the Apollo 17 landing site and areas associated with seismic activity or tectonic features, indicating that moonquakes or impacts may trigger the boulder falls.
The importance of understanding lunar surface movement
This research shows that the moon is not geologically dead but sporadically active, with multiple processes, including seismic activity, impacts, and thermal stress, causing surface changes.
The mapped hotspots of recent boulder activity could become prime landing sites for future missions aiming to study the moon’s ongoing surface and subsurface processes. This is because understanding boulder movement also helps assess surface stability, which is crucial for planning habitats, rovers, or even future mining operations.
However, the study has limitations. Detecting smaller boulder movements is still difficult, and lighting conditions can affect the visibility of ejecta patterns. While likely triggers were identified, confirming the exact cause of each boulder fall requires on-site measurements.
The researchers now plan to refine their maps further and hope future lunar missions will directly study these active sites.
The study has been published in the journal Icarus.