Evidence of Recent Geological Activity on the Moon

A new study suggests that the moon's magnetic field from a dynamo in its liquid metallic core (inner red sphere) lasted 1 billion years longer than thought. (Image credit: Hernán Cañellas (provided by Benjamin Weiss))

According to the Giant Impact Hypothesis, the Moon formed from a massive impact between a primordial Earth and a Mars-sized object (Theia) roughly 4.5 billion years ago. This is largely based on the study of sample rocks retrieved by the Apollo missions and seismic studies, which revealed that the Earth and Moon are similar in composition and structure. Further studies of the surface have revealed features that suggest the planet was once volcanically active, including lunar maria (dark, flat areas filled with solidified lava).

In the past, researchers suspected that these maria were formed by contractions in the interior that occurred billions of years ago and that the Moon has remained dormant ever since. However, a new study conducted by researchers from the National Air and Space Museum (NASM) and the University of Maryland (UMD) revealed small ridges on the Moon’s far side that are younger than those on the near side. Their findings constitute another line of evidence that the Moon still experiences geological activity billions of years after it formed.

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Every Night and Every Morning, the Moon Rumbles With Tiny Quakes

Artist's impression of astronauts on the lunar surface, as part of the Artemis Program. How will they store power on the Moon? 3D printed batteries could help. Credit: NASA
Artist's impression of astronauts on the lunar surface, as part of the Artemis Program. How will they store power on the Moon? 3D printed batteries could help. Credit: NASA

The Moon was geologically active between 3.7 and 2.5 billion years ago, experiencing quakes, volcanic eruptions, and outgassing. Thanks to the Moon being an airless body, evidence of this past has been carefully preserved in the form of extinct volcanoes, lava tubes, and other features. While the Moon has been geologically inert for billions of years, it still experiences small seismic events due to tidal flexing (because of Earth’s gravitational pull) and temperature variations. These latter events happen regularly and are known as “moonquakes.”

Thanks to the Apollo missions, scientists have measured this activity using seismometers placed on the surface. In a recent NASA-funded study, a team of researchers from the California Institute of Technology (Caltech) reexamined the seismic data with a machine-learning model. This revealed that moonquakes occur with precise regularity, coinciding with the Sun rising to its peak position in the sky and then slowly setting. In this respect, moonquakes are like a “Lunar Alarm Clock,” which could be useful for future missions and lunar settlers!

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