Did you know our Moon is shrinking? Yes, you heard that right—the Moon is getting smaller, and this could mean more moonquakes in the future. But here's where it gets controversial: while some see this as a fascinating scientific discovery, others worry about the potential risks for future lunar missions. Let’s dive into what’s happening and why it matters.
Researchers from the National Air and Space Museum's Center for Earth and Planetary Studies, along with their collaborators, have created the first-ever global map and detailed study of small mare ridges (SMRs). These subtle geological features are signs of ongoing tectonic activity on the Moon. Published in The Planetary Science Journal, their findings shed new light on how our lunar neighbor is evolving.
For the first time, scientists have shown that these ridges are relatively young and widespread across the lunar maria—the dark, broad plains visible from Earth. By understanding how SMRs form, the team has identified new potential sources of moonquakes, which could influence where future missions decide to land. And this is the part most people miss: the Moon’s shrinking isn’t just a curiosity—it’s a key to understanding its interior and predicting seismic activity.
How the Moon’s Tectonics Differ From Earth’s
Both Earth and the Moon experience tectonic forces, but they work in very different ways. On Earth, the crust is divided into moving plates that collide, pull apart, and slide past each other. These movements create mountain ranges, deep ocean trenches, and volcanic activity, especially around the Pacific Ring of Fire.
The Moon, however, doesn’t have plate tectonics. Instead, stress builds up within its single, continuous crust. This stress creates unique landforms, like lobate scarps—ridges formed when one section of the crust is pushed up and over another along a fault. These scarps are common in the lunar highlands and are relatively young, forming within the last billion years, or about the most recent 20% of the Moon’s history.
A Shrinking Moon and the Rise of SMRs
In 2010, senior scientist emeritus Tom Watters found evidence that the Moon is gradually shrinking. As its interior cools, the surface contracts, creating the compressional forces that form lobate scarps in the highlands. But lobate scarps don’t tell the whole story. Another class of landforms, small mare ridges (SMRs), has also been identified.
SMRs are formed by the same compressional forces as lobate scarps, but they appear only in the maria, not the highlands. The research team set out to map these ridges systematically and investigate their role in recent tectonic activity. Here’s the bold part: while lobate scarps have been studied since the Apollo era, SMRs were largely overlooked until now. Their widespread presence in the maria adds a crucial piece to the puzzle of lunar tectonics.
Thousands of Young Ridges Identified
The team compiled the first comprehensive catalog of SMRs, identifying 1,114 previously unrecognized segments across the near side lunar maria. This brings the total number of known SMRs to 2,634. Their analysis reveals that the average SMR is about 124 million years old—similar to the average age of lobate scarps (105 million years). This suggests that SMRs, like lobate scarps, are among the Moon’s youngest geological features.
The study also shows that SMRs form along the same types of faults as lobate scarps. In some areas, scarps in the highlands transition into SMRs in the maria, reinforcing their shared origin. Combined with existing data on lobate scarps, the new SMR catalog provides a more complete picture of the Moon’s recent contraction and tectonic evolution.
What This Means for Moonquakes and Future Missions
Earlier research by Watters linked the tectonic forces behind lobate scarps to recorded moonquakes. Since SMRs form through similar faulting, moonquakes could occur in the lunar maria wherever these ridges exist. This expanded map of potential moonquake sources gives scientists new opportunities to study the Moon’s interior and tectonic behavior.
However, it also highlights seismic risks for future astronauts. Here’s the thought-provoking question: as we plan missions like Artemis, how will we balance scientific exploration with the safety of lunar explorers? As Cole Nypaver, the study’s lead author, puts it, “We are in a very exciting time for lunar science and exploration. A better understanding of lunar tectonics will directly benefit the safety and success of future missions.”
So, what do you think? Is the Moon’s shrinking a fascinating scientific opportunity, or does it raise concerns about the challenges of lunar exploration? Let us know in the comments!
