The study, published Dec 24, 2025, in The Planetary Science Journal, was led by researchers at the National Air and Space Museum's Center for Earth and Planetary Studies and their colleagues. Their analysis shows that SMRs are distributed across the nearside maria and represent a significant component of the Moon's recent tectonic activity.
The Moon and Earth are both tectonically active, but the processes that shape their crusts differ. On Earth, the outer shell is broken into plates that collide, pull apart, and slide past one another, building mountain belts, excavating deep ocean trenches, and encircling the Pacific with a ring of volcanoes. The Moon lacks plate tectonics, yet stresses within its solid crust still generate distinct landforms, including the lobate scarps that stand as some of the most prominent contractional features in the lunar highlands.
Lobate scarps form when compressive stresses force blocks of lunar crust to thrust over adjacent terrain along faults, producing steep, cliff-like ridges. Previous work showed that these scarps are geologically young, forming within roughly the past billion years, or about the last fifth of lunar history. In 2010, Tom Watters, a senior scientist emeritus at the Center for Earth and Planetary Studies and a co-author on the new study, reported that the Moon is slowly shrinking, and that this global contraction created the lobate scarps mapped in the highlands.
Despite that earlier work, lobate scarps alone could not account for all of the Moon's young contractional landforms. The newly cataloged SMRs represent another key expression of the same underlying tectonic forces. While lobate scarps populate the highlands, SMRs appear exclusively within the maria, indicating that the Moon's shrinking interior is deforming both crustal terrains in related but morphologically distinct ways.
The research team set out to identify and characterize SMRs across the lunar maria using high-resolution imaging data. They compiled an exhaustive catalog of these features, discovering 1,114 previously unrecognized SMR segments on the nearside maria and raising the total known population to 2,634 segments globally. This expanded inventory shows that small mare ridges form an extensive and previously underappreciated network of contractional structures.
By comparing morphologies and modeling their development, the scientists found that SMRs form along the same type of thrust faults that generate lobate scarps. In many locations, lobate scarps in the highlands transition into SMRs where they cross into mare basalts, pointing to a common origin controlled by variations in crustal properties between the two terrains. Together, the lobate scarps and SMRs yield a more complete, unified picture of how the Moon has responded to internal stresses in its recent geologic past.
Age estimates derived for the ridges indicate that SMRs are young features. The average age of an SMR is about 124 million years, closely matching the roughly 105 million year average age previously reported for lobate scarps. These numbers imply that both classes of features rank among the youngest tectonic landforms on the Moon and that global contraction has continued well into relatively recent lunar 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 lead author Cole Nypaver, a post-doctoral research geologist at the Center for Earth and Planetary Studies. "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."
The findings also sharpen concern about present-day moonquakes and their implications for future human activity. Earlier work by Watters linked tectonic activity associated with lobate scarp formation to shallow moonquakes recorded by seismometers. Because SMRs arise from the same kind of contractional faulting, the new map implies that seismic events could occur across wide swaths of the maria wherever these ridges are found.
By expanding the inventory of potential moonquake sources from the highlands into the maria, the study broadens the areas where lunar seismic hazards must be considered. This enlarged hazard zone matters for the selection of landing and outpost sites for upcoming exploration campaigns, which increasingly target both polar and mid-latitude regions on the Moon.
"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. The work indicates that the Moon's interior continues to cool and contract, driving fault slip that can still generate quakes strong enough to affect the surface environment.
Nypaver noted that the discovery comes as new missions prepare to intensify exploration of the lunar surface. "We are in a very exciting time for lunar science and exploration," he 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."
The new global perspective on SMRs and their relationship to lobate scarps offers mission planners and scientists a refined framework for assessing lunar tectonic processes. It also underscores that, despite its ancient and cratered appearance, the Moon remains an active world whose interior evolution continues to shape the landscape targeted for human return.
Research Report:A New Global Perspective on Recent Tectonism in the Lunar Maria
Related Links
Smithsonian National Air and Space Museum
Tectonic Science and News
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