Apollo 11 astronaut Buzz Aldrin with the seismic experiment. Solar panels have deployed on the left and right and the antenna is pointed at Earth.  Image credit: NASA

Apollo 11 astronaut Buzz Aldrin with the seismic experiment. Solar panels have deployed on the left and right and the antenna is pointed at Earth.  Image credit: NASA

Hello Earthlings, and welcome back to another Universe Playpen blog post!

Today, let’s take a look at the first seismometer placed somewhere other than Earth! Where was that? The MOON!

The Passive Seismic Experiment was conducted from the Apollo-era, Apollo 11 to be exact! It would detect “moon quakes” and help us understand the internal structure of the Moon as well as how impact craters would effect the shaking of the ground!

Here are some more fun facts about this experiment:

1- During the 340 hour lunar night, when temperatures can plummet to minus 170ºC the instrument was kept to a minimum of minus 54ºC by a radioisotope heater, the first major use of nuclear energy in a NASA manned mission!

2- More than 1700 meteoroid impacts were recorded by the seismometer network, with impactor masses estimated to be between 0.5 and 5000 kilograms. Most moonquakes occur at depths of 800-1000 kilometers

3-These moonquakes are quite small, mostly with Richter scale magnitudes less than 2

4-Below 1000 kilometers depth, seismic wave attenuation increases, possibly indicating the presence of a small amount of molten rock!

5- More designs were improved for later seismometers that were later used at the Apollo 12, 14, 15, and 16 lunar landing sites!

Three types of moonquakes are shown here (explanation: see text). The top three rows are the recordings of a three-component long-period seismometer; the bottom row are the registriations of a short period instrument.Graphics by Yosio Nakamura, UT Austin.  Description by: UC Berkeley Seismology Lab.

Three types of moonquakes are shown here (explanation: see text). The top three rows are the recordings of a three-component long-period seismometer; the bottom row are the registriations of a short period instrument.Graphics by Yosio Nakamura, UT Austin. Description by: UC Berkeley Seismology Lab.

Thank you for reading and come back next week for a look at the latest “Living Fossil Galaxy” discovered by the Hubble Space Telescope!