Does the moon experience earthquakes (or in this case, moonquakes)? That’s one thing NASA wanted to know when we first visited our celestial companion. So when the Apollo astronauts arriv ed, they installed seismometers on the moon’s surface. Sure enough, those instruments recorded seismic events just like here on Earth. In fact, scientists have since identified four types of moonquakes: Deep, shallow, thermal and the kind stemming from meteorite impacts.

And then, analysis of the data from instruments placed by the Apollo 17 mission has recorded a fifth type — coming from the lunar lander base itself.

How could that be? Daily, the moon is subjected to extreme temperature changes — from 250 degrees Fahrenheit (121 degrees Celsius) to -208 degrees Fahrenheit (-133 degrees Celsius) during the transition from lunar day to night. Such extremes cause the lunar lander base to expand and vibrate each morning when it’s heated by the sun. “Every lunar morning when the sun hits the lander, it starts popping off,” said Allen Husker, a Caltech research professor of geophysics who worked on the project. “Every five to six minutes another one, over a period of five to seven Earth hours. They were incredibly regular and repeating.”

So what does science think of this surprising development? Although they’re being artificially generated, these tremors are still contributing to our seismic knowledge — and that’s important as we plan for future lunar expeditions.

For the complete story, see “Mysterious Moonquake Traced to Apollo 17 Lunar Lander Base” by Stefanie Waldek, at https://www.scientificamerican.com/article/mysterious-moonquake-traced-to-apollo-17-lunar-lander-base/?.