1,114 Newly Mapped Lunar Ridges Show Where Future Moonquakes May Strike
The Moon is not geologically dead. That has been clear since the Apollo seismometers recorded moonquakes in the 1970s. What has been less clear is exactly where future seismic activity is most likely to occur - a question that matters considerably more now that NASA's Artemis program is planning to put people back on the lunar surface.
A study from scientists at the Smithsonian National Air and Space Museum's Center for Earth and Planetary Studies provides the most complete answer yet. Published in The Planetary Science Journal on December 24, 2025, the research presents the first global catalog of small mare ridges (SMRs) - low, elongated tectonic features found in the dark basaltic plains called maria that cover roughly 17 percent of the Moon's near side.
1,114 New Ridge Segments
The team, led by post-doctoral research geologist Cole Nypaver with senior scientist Tom Watters as co-author, identified 1,114 new SMR segments that had not previously been documented. That discovery brings the total number of known SMR segments across the Moon to 2,634 - nearly doubling the catalog.
The average age of an SMR in the new catalog is 124 million years. That places SMRs in the same geological timeframe as lobate scarps in the lunar highlands, which Watters and colleagues previously determined averaged 105 million years old. Both are among the youngest geological features on the Moon.
The age and formation mechanism matter. Lobate scarps form when the lunar crust compresses and material is thrust upward along a fault, creating a ridge. SMRs form through the same compressional process. Critically, the researchers found that lobate scarps in the highlands often transition directly into SMRs as the terrain shifts from highland to mare - suggesting a shared structural origin rather than two distinct phenomena.
Why the Moon Is Still Shrinking
In 2010, Watters discovered that the Moon is slowly contracting as its interior cools. This thermal contraction wrinkles the crust, generating the compressional forces that produce both lobate scarps and SMRs. The process is gradual - the Moon has shrunk by roughly 50 meters in radius over geological time - but it is ongoing.
Before this study, the global picture of lunar tectonic activity was incomplete. Lobate scarps had been catalogued extensively in the highlands since the Apollo era. But the maria had not been systematically mapped for their own tectonic features. That gap meant models of lunar seismic activity were working with partial data.
"Since the Apollo era, we've known about the prevalence of lobate scarps throughout the lunar highlands, but this is the first time scientists have documented the widespread prevalence of similar features throughout the lunar mare," Nypaver said. "This work helps us gain a globally complete perspective on recent lunar tectonism."
Seismic Hazards for Future Missions
Watters had previously demonstrated a direct link between the tectonic activity that forms lobate scarps and the occurrence of shallow moonquakes. By establishing that SMRs form from the same type of faults as lobate scarps, the study extends that seismic hazard assessment to the maria. Any location near an SMR is a potential moonquake site. Several candidate Artemis landing sites are located in or near the lunar maria. The updated tectonic map provides a more complete picture of which sites may face elevated seismic risk - directly relevant to decisions about where to establish surface infrastructure and how to design structures that must withstand ground motion.
"Upcoming lunar exploration programs, such as Artemis, will provide a wealth of new information about our moon," Nypaver said. "A better understanding of lunar tectonics and seismic activity will directly benefit the safety and scientific success of those and future missions."
What Remains Unknown
The study focused on the near side of the Moon, where high-resolution imaging from NASA's Lunar Reconnaissance Orbiter Camera provided the data needed for systematic mapping. The far side was not included. Whether similar SMR populations exist on the far side, and what that implies for the Moon's global tectonic budget, remains an open question. The catalog also provides ages averaged across all identified SMRs, but the seismic hazard of any specific feature depends on whether its underlying fault remains active today - a question that current instruments cannot answer at the needed spatial resolution.