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.
What is the moon made of?
