Scientists have created sophisticated dating techniques to examine geological transformations on the far side of the moon and discovered signs of relatively recent activity.
For many years, scientists have been analyzing the moon’s surface to understand its intricate geological and developmental history. Findings from the moon’s maria—large, dark plains formed by solidified lava—indicated that the moon underwent considerable compression in its ancient history. Researchers theorized that the prominent arcs found on the near side of the moon were a result of contractions from billions of years ago, leading to the belief that the moon’s maria had been inactive since then.
However, recent research indicates that the moon’s interior might be more active than once thought. Two scientists from the Smithsonian Institution, alongside a geologist from the University of Maryland, discovered that small ridges on the moon’s far side are significantly younger than the previously examined ridges on the near side. Their research was published in The Planetary Science Journal on January 21, 2025.
“It’s widely accepted that most of the moon’s geological changes occurred between two and a half to three billion years ago,” explained Jaclyn Clark, an assistant research scientist in UMD’s Department of Geology. “However, our observations show that these tectonic features have been active recently in the last billion years and could still be changing today. These smaller mare ridges appear to have formed within the last 200 million years, which is quite recent when considering the moon’s long history.”
By employing cutting-edge mapping and modeling methods, the team identified 266 previously unknown small ridges on the far side of the moon. These ridges typically formed in clusters of 10 to 40 within volcanic zones that likely originated 3.2 to 3.6 billion years ago, pinpointed in areas that may have structural weaknesses. To determine the age of these ridges, the researchers utilized a technique called crater counting, which revealed that these ridges were much younger than their well-known neighboring features.
“In essence, the more craters present on a surface, the older it is; that surface has had more time to accumulate craters,” Clark clarified. “After counting the craters surrounding these small ridges and noting that some ridges intersect existing impact craters, we conclude that these landforms have experienced tectonic activity in the last 160 million years.”
Moreover, Clark mentioned that the ridges on the far side showed similarities to those on the near side, implying they were created by similar geological forces, likely linked to the gradual contraction of the moon and changes in its orbit. Previously observed shallow moonquakes during the Apollo missions now appear to be connected to the development of these small ridges due to similar seismic activities. Understanding the evolution of the moon’s surface may significantly influence the planning of future lunar missions.
“We anticipate that upcoming moon missions will incorporate technologies such as ground-penetrating radar to enable a deeper exploration of the structures beneath the moon’s surface,” Clark added. “Recognizing that the moon is still geologically active has tangible consequences for selecting locations to establish our astronauts, equipment, and infrastructure on the lunar surface.”
