Mapping Small Mare Ridges: A New Understanding of Lunar Tectonics

Recent research has produced the first global map and detailed analysis of small mare ridges (SMRs) on the Moon, revealing significant insights into its tectonic activity. Conducted by scientists from the National Air and Space Museum's Center for Earth and Planetary Studies, the findings, published in *The Planetary Science Journal*, indicate that these geological features are relatively young and widespread across the lunar maria, the dark plains visible from Earth. This study not only enhances our understanding of the Moon's geological history but also identifies potential sources of moonquakes, which could impact future lunar exploration missions.

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The research team cataloged 1,114 previously unrecognized SMR segments, bringing the total known SMRs to 2,634. The average age of these ridges is approximately 124 million years, closely aligning with the average age of lobate scarps—another tectonic feature on the Moon—at 105 million years. Both SMRs and lobate scarps form from compressional forces within the Moon's single, continuous crust, which contrasts with Earth's plate tectonics. The identification of SMRs contributes to a more complete understanding of the Moon's recent contraction and tectonic evolution, suggesting that the Moon may have experienced more global contraction than previously thought.

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The presence of SMRs indicates potential moonquake activity across the lunar maria, similar to that associated with lobate scarps. This expanded understanding of tectonic features provides new opportunities for studying the Moon's interior and seismic behavior. Cole Nypaver, a postdoctoral research geologist and lead author of the study, emphasized that this research offers a globally complete perspective on lunar tectonism, which is crucial for assessing risks for future lunar missions.

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The research team highlighted the importance of their findings for upcoming lunar exploration programs, such as NASA's Artemis missions. Nypaver stated, "Our results represent the most globally complete understanding of recent lunar tectonism to date." Tom Watters, a senior scientist involved in the study, noted that understanding lunar tectonics and seismic activity will directly benefit the safety and scientific success of future missions.

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While the study presents a significant advancement in lunar science, some experts caution that the implications of moonquakes for long-term lunar habitation must be carefully considered. The potential hazards posed by seismic activity could complicate plans for establishing permanent lunar outposts.

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As NASA prepares for its Artemis II mission, set to launch in March 2024, future missions will focus on landing astronauts on the lunar surface and establishing infrastructure. The Lunar Environment Monitoring Station, part of Artemis 3, will monitor seismic activity, providing critical data on tectonics-related risks. Additionally, private companies are exploring lunar mining opportunities, emphasizing the need for a thorough understanding of the Moon's geological features to inform site selection for future operations.

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• “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,” — Cole Nypaver, Postdoctoral Research Geologist

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• “Our detection of young, small ridges in the maria, and our discovery of their cause, completes a global picture of a dynamic, contracting moon,” — Tom Watters, Senior Scientist Emeritus

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• “The presence of these additional tectonic features in the lunar maria suggests that the moon may have experienced more global contraction in the recent past than previously thought.” — Cole Nypaver, Postdoctoral Research Geologist

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