Scientists have mapped thousands of young tectonic ridges across the Moon, showing it is still slowly shrinking. These ridges may mark previously unknown sources of moonquakes.
Scientists have completed the first worldwide map and detailed study of small mare ridges (SMRs), subtle surface features that signal tectonic activity on the Moon. The research, published in The Planetary Science Journal, was led by scientists at the National Air and Space Museum’s Center for Earth and Planetary Studies along with collaborators.
For the first time, the team shows that SMRs are relatively young and widely distributed across the lunar maria, the broad, dark plains visible from Earth. By identifying how these ridges form, researchers have also uncovered new potential sources of moonquakes that could influence where future missions choose to land.
How Lunar Tectonics Differ From Earth
Earth and the Moon are both tectonically active, but the mechanisms behind that activity are very different. On Earth, the crust is divided into moving plates that collide, separate, and slide past one another. Those interactions create mountain ranges, deep ocean trenches, and the chain of volcanoes surrounding the Pacific.
The Moon does not have plate tectonics. Instead, stress builds within its single outer shell. That stress produces distinctive landforms. Among the most common are lobate scarps, ridges created when the crust compresses, and one block of rock is thrust over another along a fault. These features are common in the lunar highlands and formed within the last billion years, representing about the most recent 20% of the Moon’s history.
A Shrinking Moon and the Origin of SMRs
In 2010, co-author Tom Watters, a senior scientist emeritus at the Center for Earth and Planetary Studies, reported that the Moon is gradually shrinking. As its interior cools, the surface contracts, creating compressional forces that formed lobate scarps in the highlands.
However, those scarps do not account for all recent contraction features. Another category of tectonic structures, small mare ridges, has also emerged as an important piece of the puzzle.
SMRs form from the same compressional forces responsible for lobate scarps. The key difference is location. Lobate scarps are found in the highlands, while SMRs occur only in the maria. The research team set out to systematically map these ridges across the maria and evaluate their role in the Moon’s recent tectonic history.
“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,” said Cole Nypaver, a post-doctoral research geologist at the Center for Earth and Planetary Studies and the first author on the paper. “This work helps us gain a globally complete perspective on recent lunar tectonism on the moon, which will lead to a greater understanding of its interior and its thermal and seismic history, and the potential for future moonquakes.”
Thousands of Young Ridges Identified
The team assembled the first comprehensive catalog of SMRs. In doing so, they identified 1,114 previously unrecognized SMR segments across the near side lunar maria. That raises the total number of known SMRs on the Moon to 2,634.
Their analysis indicates that the average SMR is about 124 million years old. That closely matches the average age of lobate scarps (105 million years old) reported in earlier work by Watters and colleagues. These comparable ages suggest that SMRs, like lobate scarps, are among the youngest geological features on the Moon.
The study also found that SMRs formed along the same types of faults as lobate scarps. In several areas, highland scarps transition into SMRs within the maria, reinforcing the idea that both structures share a common origin. When combined, the data on scarps and SMRs provide a far more complete view of the Moon’s recent contraction and tectonic activity.
“Our detection of young, small ridges in the maria, and our discovery of their cause, completes a global picture of a dynamic, contracting moon,” Watters said.
Expanding the Map of Moonquake Risk
Earlier research by Watters linked the tectonic forces that form lobate scarps with recorded moonquakes. Because SMRs arise from the same type of faulting, the findings suggest that moonquakes could also occur throughout the lunar maria wherever these ridges are present.
Identifying additional potential quake sources improves scientists’ ability to study the Moon’s interior and tectonic behavior. At the same time, it highlights possible seismic risks for astronauts who may one day explore or live on the lunar surface.
“We are in a very exciting time for lunar science and exploration,” Nypaver said. “Upcoming lunar exploration programs, such as Artemis, will provide a wealth of new information about our moon. A better understanding of lunar tectonics and seismic activity will directly benefit the safety and scientific success of those and future missions.”
Reference: “A New Global Perspective on Recent Tectonism in the Lunar Maria” by C. A. Nypaver, T. R. Watters, M. E. Banks, J. D. Clark and T. Frueh, 24 December 2025, The Planetary Science Journal.
DOI: 10.3847/PSJ/ae226a
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The Sun will appear much smaller than the Moon in the sky in a few billion years. The Moon will become slightly larger in a few billion years because two large spiral arms of the galaxy collide with objects in the Solar System every 65 million years. During each half rotation of these large spiral arms around the galactic core, objects from the Milky Way galaxy will collide with objects in the Solar System, and several thousand meters of material from Milky Way objects will settle on the surface of the Moon.