Lunar Mare Ridges: Unveiling a Dynamic, Contracting Moon and New Moonquake Zones

Scientists have created the first global map and analysis of small mare ridges (SMRs) on the Moon. This groundbreaking study, published in The Planetary Science Journal on December 24, 2025, indicates that SMRs are geologically young and are widespread across the Moon's vast, dark plains, known as lunar maria. The discovery of how SMRs form suggests new potential sources for moonquakes, which could influence future lunar landing site selections.

Understanding Lunar Tectonics

Both the Moon and Earth exhibit tectonic activity, though the underlying forces and mechanisms differ significantly. Earth's crust is divided into multiple plates that constantly move and interact, while the Moon's crust is not. However, stresses within the lunar crust still create distinct landforms.

One such landform is the lobate scarp, which forms when the lunar crust compresses, pushing material over adjacent crust along a fault. These scarps are typically found in the lunar highlands and have formed within the last billion years.

In 2010, scientist Tom Watters identified that the Moon is slowly contracting, leading to the formation of these scarps.

The Discovery of Small Mare Ridges (SMRs)

SMRs represent another class of recently identified tectonic landforms on the Moon. They result from the same powerful forces that create lobate scarps but are exclusively found in the maria. The research team's primary aim was to map SMRs across the lunar maria and analyze their connection to recent tectonic activity.

Cole Nypaver, a post-doctoral research geologist and first author of the study, highlighted the significance of this work.

"While lobate scarps in the highlands have been known since the Apollo era, this is the first documentation of similar widespread features in the lunar mare."

This work, Nypaver added, contributes to a global understanding of recent lunar tectonism, providing crucial insights into the Moon's interior, its thermal and seismic history, and the potential for future moonquakes.

Key Research Findings and Shared Origins

The team compiled an extensive catalog of SMRs, identifying 1,114 new SMR segments across the nearside lunar maria. This brings the total known SMRs to 2,634. The average age of SMRs was determined to be 124 million years, consistent with the average age of lobate scarps (105 million years), placing SMRs among the youngest geological features on the Moon.

The analysis further indicates that SMRs formed via the same type of faults as lobate scarps. Notably, lobate scarps in the highlands often transition to SMRs in the mare, implying a shared origin and a continuous process across different lunar terrains. This data, combined with existing knowledge of lobate scarps, offers a more comprehensive view of recent contractional tectonic activity on the Moon.

Tom Watters noted that "the detection of young, small ridges in the maria and the discovery of their cause complete a global picture of a dynamic, contracting Moon."

Implications for Moonquakes and Future Exploration

Previously, a link was established between the tectonic activity causing lobate scarps and the incidence of moonquakes. The new finding that SMRs originate from the same type of tectonic activity suggests that moonquakes could also occur across the lunar maria, wherever an SMR is present.

This expansion of potential moonquake sources creates valuable opportunities for better understanding lunar tectonics. Simultaneously, it indicates an elevated seismic risk for future human exploration or habitation on the Moon.

Nypaver commented on the practical significance for upcoming missions: "Upcoming lunar exploration programs, such as Artemis, will provide new information about the Moon, and a better understanding of lunar tectonics and seismic activity will benefit the safety and scientific success of these missions."