Lost sight of Apollo data from the 1970s finds gigantic reveal of ‘hidden’ moonquakes

Understanding Moonquakes: How They Differ from Earthquakes

Moonquakes are seismic events occurring on the lunar surface caused by movements within the moon’s interior. Unlike earthquakes, which primarily result from the shifting of tectonic plates, the moon lacks such plate tectonics. Instead, moonquakes arise from factors such as gradual temperature fluctuations, tidal stresses caused by Earth’s gravitational pull, and meteorite impacts.

Because the moon’s interior dynamics differ significantly from Earth’s, moonquakes tend to be weaker than terrestrial earthquakes. The moon’s lack of atmosphere and tectonic plates means seismic events are generally less intense but can last longer due to the moon’s rigid crust and lack of water to dampen vibrations. Despite their relative weakness, moonquakes provide vital clues about the moon’s internal structure, thermal evolution, and ongoing geological processes. Understanding these quakes is essential for assessing the moon’s stability and safety for future human activities.

Apollo Missions and the Original Seismic Data

Between 1969 and 1977, Apollo astronauts deployed two types of seismometers on the lunar surface. One type was designed to capture long-duration seismic waves in three dimensions, capable of monitoring subtle movements over extended periods. The other type recorded short-duration, rapid shaking events, capturing transient seismic activity.

The initial analysis of Apollo data focused almost exclusively on the long-duration recordings, which identified approximately 13,000 moonquakes. The short-duration data, however, was largely neglected due to significant interference caused by extreme temperature swings between lunar day and night and technical challenges in transmitting data back to Earth. These factors introduced noise and made it difficult to interpret the short-duration signals reliably.

After the Apollo missions ended, NASA shifted funding away from lunar seismology to support other initiatives, leading to the abandonment and partial loss of the short-duration data sets. This data was nearly lost forever, as it was stored on fragile media and not prioritized for preservation.

Rediscovering Lost Data: The Path to New Discoveries

In a remarkable effort to recover lost information, retired geophysicist Yosio Nakamura preserved a copy of the short-duration Apollo data on 12,000 reel-to-reel tapes. These tapes were later digitized, making the data accessible for modern computational analysis.

Seismologist Keisuke Onodera of the University of Tokyo undertook a painstaking three-month review of this digitized data. Using advanced denoising techniques to filter out interference from temperature fluctuations and transmission noise, Onodera identified approximately 30,000 moonquake candidates.

Further analysis confirmed that 22,000 of these events were genuine lunar quakes, nearly tripling the previously known total and revealing a much more seismically active moon than scientists had assumed. This finding underscores the value of revisiting archival data with modern technology, which can yield transformative insights even decades after initial collection.

Implications of the New Findings for Lunar Geology

The expanded catalog of moonquakes suggests that the moon’s seismic activity is not only more frequent but also more complex than previously understood. Notably, many of the newly identified quakes appear to originate at shallower depths than earlier estimates suggested.

This observation hints at fault-oriented mechanisms driving these seismic events, challenging the earlier view that moonquakes were primarily caused by deep interior processes such as thermal contraction and tidal stresses. Instead, the data suggests a more active tectonic environment with shallow faults that may be slipping and causing seismic activity.

These findings open new avenues for understanding lunar tectonics and the moon’s geologic evolution. However, confirming these theories will require additional data and future missions equipped with advanced seismic instruments to monitor the moon’s interior dynamics in greater detail.

Future Lunar Missions and the Role of Seismology

Recent and upcoming lunar missions promise to enhance our understanding of moonquakes and the moon’s seismic environment. For example, in August 2023, India’s Chandrayaan-3 mission detected the first moonquake since the Apollo era, signaling renewed interest and capability in lunar seismology.

NASA and commercial partners are planning to deploy new seismometers on the moon. The Intuitive Machines’ Odysseus lander, which successfully reached the lunar surface in February 2024, is among the first U.S. landers in over five decades to carry instruments capable of seismic measurements.

These modern instruments will help validate the recent discoveries from Apollo data and provide continuous monitoring, essential for understanding the moon’s seismic environment. This knowledge is crucial for designing safe lunar habitats and infrastructure, as seismic activity could impact construction and long-term human presence on the moon.

Moreover, improved seismic data will contribute to broader planetary science, offering insights into the geological processes of other celestial bodies without active plate tectonics, such as Mars and Mercury.

What this means

The rediscovery and reanalysis of Apollo-era seismic data have dramatically reshaped our understanding of the moon’s seismic activity. Far from being a geologically inert body, the moon exhibits a dynamic seismic environment with thousands of previously hidden moonquakes. These revelations not only enrich lunar science but also carry practical significance for future exploration and habitation efforts. As new missions deploy advanced seismometers, scientists anticipate gaining even deeper insights into the moon’s internal processes, paving the way for safer and more sustainable human presence on our celestial neighbor.