Apollo-Era Seismometers Reveal 22,000 New 'Moonquakes' Decades Later

Astronauts during the Apollo missions between 1969 to 1977 installed seismometers on the Moon, detecting about 13,000 moonquakes. Back then, those moonquakes were the sole lunar seismic events documented.

Apollo Seismic Data Analysis Reveals Surprising Moonquake Activity

During the Apollo missions, astronauts deployed two types of seismometers on the lunar surface: one capable of monitoring seismic wave motion in three dimensions over extended periods, and another designed to detect rapid shaking over shorter durations.

As researchers meticulously reanalyzed some of the data from Apollo missions, they found an additional 22,000 moonquakes, almost thrice the number of the initial moonquakes recorded.

In their study, titled "New Views of Lunar Seismicity Brought by Analysis of Newly Discovered Moonquakes in Apollo Short-Period Seismic Data" under review by the Journal of Geophysical Research, the team underscores the Moon's unexpected seismic activity and emphasizes the significance of revisiting historical data to learn fresh scientific revelations.

Moonquakes occur due to movements within the Moon's interior, driven by gradual temperature changes and meteorite impacts, rather than tectonic plate shifts, as the moon lacks them according to NASA. As a consequence, moonquakes are significantly less intense than their terrestrial counterparts.

Jeffrey Andrews-Hanna, a geophysicist at the University of Arizona not involved in the study, remarked on the potential implications of these findings, suggesting that they indicate a higher level of seismic and tectonic activity on the moon than previously believed. He expressed his surprise at the continuous emergence of new insights from data even after five decades.

The findings of the study were recently presented during the Lunar and Planetary Science Conference held in Texas from March 13 to March 17.

Moonquakes: Understanding Lunar Seismic Activity and Its Differences from Earthquake

Moonquakes, resembling seismic activities on Earth, represent unique surface vibrations on the Moon. These disturbances stem from distinct causes, including lunar contraction and cooling, influenced by gravitational forces or Earth's pull, resulting in fissures and subsequent quakes.

Additionally, meteor impacts contribute to moonquakes by generating substantial surface disturbances. Four primary types of moonquakes exist deep, shallow, thermal, and meteorite-induced vibrations, each originating from different mechanisms and occurring at various depths within the Moon's interior or surface.

Detection and analysis of moonquakes are facilitated by seismometers deployed during the Apollo missions, stationed on the lunar surface. These instruments continuously monitor tremors and vibrations, capturing movements when moonquakes occur.

Subsequently, recorded data is transmitted back to Earth via radio signals or alternative methods like laser beams. Scientists meticulously scrutinize this data to extract valuable insights into moonquake characteristics, such as magnitude and epicenter location, aiding in understanding lunar seismic activity.

Moonquakes, in contrast to earthquakes, exhibit considerably lower magnitudes and potential impact levels. While earthquakes on Earth can register magnitudes surpassing 9.0 on the Richter scale, with varying degrees of destructiveness, moonquakes generally range from approximately 2.0 to 5.5 on the Richter scale.

Consequently, moonquakes pose significantly lower risks in terms of harm and damage potential compared to their terrestrial counterparts, highlighting the relatively subdued seismic activity on the Moon.