MOONQUAKES

the MOON RINGS LIKE a BELL
https://nasa.gov/podcasts/music-of-the-spheres
https://popularmechanics.com/hollow-moon-theory
https://popsci.com/does-moon-sound-like-bell
Does the Moon Sound Like a Bell?
by Amy Shira Teitel / May 27, 2016

“Though the Apollo lunar modules were built for the sole purpose of landing two men on the surface of the Moon, their usefulness didn’t end after ascending from the lunar surface. NASA used the spent spacecraft for science, directing these modules for controlled crashed into the Moon. These crashes caused moonquakes, and scientists measured the vibrations moving through the Moon and found it rings like a bell. The real goal of the seismic experiments was to figure out the Moon’s internal structure. Measuring how long the reverberations last, how powerful they are, and how big the waves get can reveal what the Moon is made of.

Remote seismic stations were instrumental in this investigation, and they were deployed as part of the Apollo Lunar Surface Experiment Packages that astronauts set up on the Moon on Apollos 12, 14, 15, and 16; different versions were deployed on Apollos 11 and 17. From when they were first set up to when they were remotely shut down in 1977, these ALSEPs recorded all kinds of seismic activity. The data was sent back to receiving stations on Earth where the signal was magnified by 10 million so scientists could interpret the signal. But something interesting happened on Apollo 12. After Pete Conrad and Al Bean landed at the Ocean of Storms on November 14, 1969, they left the lunar surface 142 hours into the flight. Eight hours later, they were reunited with Dick Gordon in the command module and sent their spent lunar module back to the Moon.

It impacted about 40 miles away from the Apollo 12 landing site with the force of one ton of TNT. The resulting shockwave built up and peaked in just eight minutes. Then it took an hour to fully dissipate. Something similar happened on Apollo 13. The S-IVB impacted the Moon 85 miles from Apollo 12’s ALSEP — CMP Jack Swigert joked at the time that it was the only thing on that mission to go right. It hit with the force of 11 and a half tons of TNT. This translated to a seismic impact peaked after seven minute with shockwaves 30 times greater and four times longer than those from Apollo 12’s LM impact. The vibrations from these two impacts lasted longer than scientists expected, far longer than any equivalent vibrations last on Earth. It was almost as if the Moon was ringing like a bell. This strange result forced scientists to think differently about the Moon and its composition.

It turns out that these impacts were characteristic of one of four types of moonquakes scientists studied from ALSEP data. Some moonquakes originate deep below the surface because of lunar tides, some are thermal quakes caused by the Sun thawing the frozen surface at the start of a new lunar day, and others are caused by impacting meteors. The fourth kind of moonquake is a shallow moonquake occurring roughly a couple of tens of miles below the surface. The lunar module and S-IVB both produced this kind of vibration, and these are the most violent types of moonquakes.

Between 1972 and 1977, scientists recorded 28 shallow moonquakes registering as high as 5.5 on the Richter scale. On Earth, that will move heavy furniture and crack plaster, but the vibrations usually die down in a matter of minutes. It all comes down to water. There’s moisture in the materials that makes up our planet, expanding their structure. As energy from an earthquake moves through our planet, that damp material acts like a sponge, absorbing the energy of the waves and ultimately deadening their effects. But the Moon is dry, cool, and rigid, more like a solid rock than a sponge. So even if a moonquake is less intense, there’s nothing to deaden the vibrations. They just go back and forth through the body until the solid stone eventually stops them. The “ringing bell” is the shock waves reverberating through that stone.”

MOONQUAKES
https://science.nasa.gov/moonquakes
https://phys.org/news/2025-08-moon.html
What is the moon made of?
by Paul Sutter, edited by Lisa Lock, reviewed by Robert Egan / August 25, 2025

“A set of instruments shut off almost 50 years ago are still producing useful results. It’s the seismometers left by the Apollo missions to monitor moonquakes, which, as the name suggests, are earthquakes but on the moon. First off, the Apollo seismometers were the first to reveal that the moon does indeed have quakes, which is an impressive achievement in its own right. And once we realized that the moon shakes, we’ve been able to use the natural seismic vibrations produced inside the moon to map out its interior structure.

It’s the same way that we can map out the interior of Earth. Vibrations travel at different speeds through different kinds of materials, just like sounds are different in the air versus underwater. The reason that the Apollo-era seismometers, which were shut off in 1978, still provide useful results is that even though they’re not producing data, our analysis techniques and understanding have improved. This means we can squeeze more information out of the data we already have, and decades after the seismometers went silent, we were able to use their data to find evidence for the existence of the moon’s core.

So the moon’s got a core, that’s nice. What’s the big deal? The big deal is that it’s best to stop thinking of the moon as merely the natural satellite of Earth. Instead, think of it as a small rocky terrestrial world in its own right. It’s stepping out of the shadow and into the limelight, and it’s got something to say. I’m reframing this because the moon is our keystone to understanding how ALL terrestrial planets — Mercury, Venus, Mars, and yes, even Earth—evolved in their early history. That’s because the moon still retains a record, a memory, of its younger days, frozen in place for billions of years. Earth doesn’t remember most of its ancient history because of all our plate tectonics. We haven’t landed on Mercury. We’ve technically landed on Venus, but that wasn’t for very long, so it doesn’t count. And yes, we’ve landed a lot on Mars, and even collected some samples…but we haven’t figured out how to get those samples back to Earth.

So not only does the moon retain a memory of what all terrestrial planets go through, it’s right there and we’ve been able to touch it! And bring some back! And, and smell it! By cracking open moon rocks, by looking at seismometer data, by looking at core samples, by looking at heat flow data, we can piece together what happened on the moon and use that knowledge to inform what happens to Mars, Venus, Mercury…and Earth. And what happened to the moon was, put simply, not very pretty. We now know that there was a phase, shortly after it formed, when the moon was covered in a single magma ocean with a depth of around 500 kilometers.

What we call the lunar highlands are simply the slightly-less-dense rock that floated to the surface of that magma ocean and then solidified first. What floated to the top and cooled was largely minerals containing oxygen and silicon, with iron sinking down to form the core—hey wait a minute, that’s exactly like Earth! I told you the moon could tell us about our own planet. Shortly after the surface of the moon largely cooled and the crust formed, it suffered a series of intense impacts, an epoch between 3.85 and 4 billion years ago called the Late Heavy Bombardment. Just strike after strike after strike, like a brutal uneven boxing match that you just can’t look away from. Each of those impacts formed breccias, which comes from the Italian word for rubble.

“A petrographic thin section of Apollo 17 sample 72275,
a fragmental breccia. Credit: Randy Korotev”

Why we didn’t just call it rubble, I don’t know. Breccias are formed when you have a bunch of different kinds of rocks and minerals doing their own thing, minding their own business, when WHAM a meteorite comes crashing in, smashing and mixing and fusing everything together, and then all those minerals are forced to cohabitate in the same rocks. Finally, after the late heavy bombardment, the moon suffered periods of major volcanism, which would explode and pour liquid hot magma across their surroundings, generating the mare, or seas, that we see today.”

“Chang’e-6 basaltic fragment. Credit: Beijing SHRIMP Center, Institute of Geology, CAGS”

OCEANS of MAGMA
https://science.org/doi/10.1126/science.adt3332
https://phys.org/lunar-side-samples-bolster-theory
Lunar far side samples bolster theory that moon was once covered in magma
by Bob Yirka / March 19, 2025

“A team of geologists at the Chinese Academy of Geological Sciences, the Institute of Space Sciences and the Shandong Institute of Geological Sciences, all in China, has found evidence in soil samples collected from the far side of the moon that bolsters a theory that the moon was once covered by an ocean of magma.

“Image captured by the panoramic camera of the Chang’e 6 lander. Credit: CNSA Lunar Exploration and Space Engineering Center”

In their study published in the journal Science, the group analyzed a moon soil sample returned to Earth by China’s Chang’e-6 mission. In 2024, the China National Space Administration launched a spacecraft that carried a lander to the surface of the far side of the moon. The mission was the first to collect samples from the far side of the moon and return them to the Earth. For this new study, the research team obtained 2 grams of the soil for testing.

“Chang’e-6 Landing site. Credit: Beijing SHRIMP Center, Institute of Geology, CAGS”

The researchers used multiple methods to determine its composition and then compared the results to those of analyses of soil samples from the near side of the moon. The researchers found that the basalt in the sample was similar to basalt found in samples collected from the near side of the moon—the ratios of isotopes were similar. They also found similarities in age. These findings bolster theories that during the moon’s early years, it was covered by an ocean of magma.

The magma ocean model suggests the moon experienced a massive melting event during its infancy, which led to the creation of a magma ocean. Then, as the magma cooled and crystallized, the densest material sank to form the mantle, while the least dense material floated to the top, leaving it on the surface when the ocean solidified. Types of materials mixed and formed what has come to be known as the KREEP layer, named after its primary components. Moon samples collected from both the far and near sides were KREEP samples.

“Lunar soil from Chang’e-6 landing site. Credit: Beijing SHRIMP Center, Institute of Geology, CAGS”

Because of such strong similarities between them, the odds are good that they were formed in the same way, suggesting the magma ocean stretched across to the moon’s far side and likely covered the entire moon, adding credence to the ocean magma theory. The researchers note that there were some differences in the isotopes, which they suggest are likely due to differences in evolutionary history after the magma ocean solidified.

“Image captured by the landing camera of the Chang’e 6 lander-2. Credit: CNSA Lunar Exploration and Space Engineering Center”

More information: Xiaochao Che et al, Isotopic and compositional constraints on the source of basalt collected from the lunar far side, Science (2025). DOI: 10.1126/science.adt3332

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