Moonquakes: Evidence of Ongoing Tectonic Activity on the Moon
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Chapter 1: The Moon's Quaking Mystery
Recent analyses reveal that the Moon is still in a state of tectonic activity, with new findings suggesting that it is continuing to shrink. Data from NASA’s Apollo missions, along with observations from the Lunar Reconnaissance Orbiter (LRO), have provided insights into these ongoing changes.
In 2010, a study of images from the LRO indicated that the Moon's surface had developed thousands of cliffs, known as thrust faults, due to its cooling interior. A more recent investigation, led by geologist Nicholas Schmerr from the University of Maryland, builds upon this discovery, suggesting that not only is the Moon shrinking, but it is also actively generating moonquakes along these faults.
Section 1.1: Understanding Thrust Faults
The thrust faults identified by the LRO resemble stair-like cliffs, or scarps, which form when sections of the Moon's crust are forced upward as the interior cools and contracts. New research indicates that these geological features may still be active, as evidenced by landslides and movement of boulders.
Schmerr noted, “Our analysis showed that many recorded quakes in the Apollo data occurred near these thrust faults. It’s quite possible that these faults remain active, which is exciting since active tectonics are rare beyond Earth.”
The research team utilized a newly developed algorithm to re-evaluate seismic data collected by instruments deployed during the Apollo missions in the 1960s and 1970s. This re-analysis allowed them to accurately determine the epicenters of 28 recorded moonquakes from 1969 to 1977.
Subsection 1.1.1: Pinpointing Epicenters
By overlaying this refined data onto LRO images, the researchers discovered that at least eight of the moonquakes were closely linked to tectonic activity along the thrust faults, rather than being the result of asteroid impacts or other internal rumblings.
Although the last recorded quake by Apollo instruments was in 1977, the researchers believe that the Moon is still experiencing seismic events today, as indicated by a paper published in Nature Geoscience on May 13, 2019.
Section 1.2: The Mechanism Behind Moonquakes
Astronauts installed five seismometers on the lunar surface during various Apollo missions. While the Apollo 11 seismometer only operated for a brief period, the remaining instruments detected 28 shallow moonquakes—indicative of tectonic faults—between 1969 and 1977. On Earth, these quakes would have had magnitudes ranging from approximately 2 to 5.
The researchers found that six of the eight identified quakes occurred when the Moon was at or near its apogee, the point furthest from Earth in its orbit. At this distance, the Moon experiences increased tidal stresses, making it more susceptible to slippage along the thrust faults.
Thomas Watters, the lead author and senior scientist at the Smithsonian Institution's Center for Earth and Planetary Studies, stated, “It’s very likely that these quakes were caused by the faults slipping due to stress from global contraction and tidal forces, indicating the Moon is still tectonically active.”
Chapter 2: Moon's Shrinking Process
The researchers drew an analogy between the Moon's geological process and that of a grape drying into a raisin. As the Moon's interior cools and contracts, it develops wrinkles, or faults, similar to how a grape's skin wrinkles as it dries out. Unlike the flexible skin of a grape, the Moon’s crust is brittle, leading to breaks and the formation of thrust faults.
The LRO has captured images of over 3,500 fault scarps since its launch in 2009, revealing fresh landslides and boulders at the bases of these features. These brighter areas indicate regions newly exposed by geological events like moonquakes.
The first video, titled "NASA says the moon is shrinking and experiencing 'moonquakes'", provides a detailed overview of the Moon's current geological state and the implications of these findings.
The research team aims to compare images from different times to search for fresh signs of moonquake activity. Schmerr emphasizes the need for renewed lunar exploration, stating, “The Apollo missions taught us a lot, but there is still so much more to discover.”
The second video, "Is Earth in Danger as the Moon Shrinks?", discusses potential implications of the Moon's geological changes on Earth.
In conclusion, the study titled “Shallow seismic activity and young thrust faults on the Moon,” co-authored by Schmerr and published in Nature Geoscience, highlights the Moon's ongoing tectonic activity and underlines the importance of future lunar missions for advancing our understanding of its geology.