Recent studies have brought to light that the Moon's seismic activity is far more intense than previously thought.
By revisiting overlooked data from NASA's Apollo missions, scientists have discovered over 22,000 previously unknown lunar quakes, nearly tripling the total number of seismic events identified on our natural satellite.
Lunar quakes, or selenoseisms, occur due to movements within the Moon, similar to earthquakes on Earth. However, unlike the latter, selenoseisms are mainly caused by temperature variations and meteorite impacts since the Moon does not have tectonic plates. These quakes are generally less intense than those on Earth.
During the Apollo missions, between 1969 and 1977, about 13,000 selenoseisms were recorded. A new analysis has, however, uncovered an additional 22,000 quakes, bringing the total to 35,000. This reassessment work has revealed that the Moon could be more seismically active than previously thought, hinting at unknown surprises in the 50-year-old data.
The Apollo astronauts had deployed two types of seismometers on the Moon, one recording seismic movements in 3D over long periods, and the other capturing rapid shakes over short periods. It is this short-period data, long neglected due to interference, where a significant portion of the new selenoseisms was identified.
Buzz Aldrin deploying the first lunar seismometer during the Apollo 11 mission. Credit: NASA These discoveries suggest that some of these quakes could originate from shallower points than previously thought, which could alter our understanding of the mechanisms behind these quakes. However, more data is needed to confirm these hypotheses.
Recent and future lunar missions could help scientists better understand selenoseisms. In August 2023, Vikram lander of India's Chandrayaan-3 mission detected the first selenoseism since the Apollo missions, marking a significant advancement in our knowledge of lunar seismic activity.
The findings of this study were presented at the Lunar and Planetary Science Conference and are under revision by the
Journal of Geophysical Research.