

When Part of Apollo 13 Reached the Moon - ColinWright
http://news.discovery.com/space/history-of-space/when-part-of-apollo-13-reached-the-moon-130516.htm

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netcraft
So, is there natural seismic activity on the moon? Apparently so:
[http://www.wired.com/wiredscience/2012/02/moon-seismology-
ea...](http://www.wired.com/wiredscience/2012/02/moon-seismology-earthquakes/)
but i'm having trouble finding anyone talking about results from these
installed seismic sensors.

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3JPLW
Here's a great link that talks about data from these seismometers:
[http://www.nasa.gov/exploration/home/15mar_moonquakes_prt.ht...](http://www.nasa.gov/exploration/home/15mar_moonquakes_prt.htm)

Some relevant quotes:

 _'There are at least four different kinds of moonquakes: (1) deep moonquakes
about 700 km below the surface, probably caused by tides; (2) vibrations from
the impact of meteorites; (3) thermal quakes caused by the expansion of the
frigid crust when first illuminated by the morning sun after two weeks of
deep-freeze lunar night; and (4) shallow moonquakes only 20 or 30 kilometers
below the surface.'_

...

 _'Furthermore, shallow moonquakes lasted a remarkably long time. Once they
got going, all continued more than 10 minutes. "The moon was ringing like a
bell," Neal says.

'On Earth, vibrations from quakes usually die away in only half a minute. The
reason has to do with chemical weathering, Neal explains: "Water weakens
stone, expanding the structure of different minerals. When energy propagates
across such a compressible structure, it acts like a foam sponge--it deadens
the vibrations." Even the biggest earthquakes stop shaking in less than 2
minutes.

'The moon, however, is dry, cool and mostly rigid, like a chunk of stone or
iron. So moonquakes set it vibrating like a tuning fork. Even if a moonquake
isn't intense, "it just keeps going and going," Neal says. And for a lunar
habitat, that persistence could be more significant than a moonquake's
magnitude.'_

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Edit: Aha! I wonder if it was Werner Von Braun who first said the moon "rang
like a bell." That was the search phrase I used to find the above. Here's a
really cool article by him in Popular Science from 1970, talking specifically
about the impact from Apollo 12's Lunar Module [2].

 _"The object of the deliberate crash was to see what the instrument would
report to earth, and the result astounded scientists. The moon rang like a
bell!"_

[1]
[http://www.nasa.gov/exploration/home/15mar_moonquakes_prt.ht...](http://www.nasa.gov/exploration/home/15mar_moonquakes_prt.htm)

[2] [http://books.google.com/books?id=VQEAAAAAMBAJ&lpg=PA62&#...</a>

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scrumper
I wonder where the spent S-IVB stages from the three previous missions are,
right now?

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3JPLW
They're in some sort of heliocentric orbit [1]. They didn't track them.

One's been rediscovered, initially designated as asteroid J002E3 [2].

[1] <https://en.wikipedia.org/wiki/S-IVB#Stages_built>

[2] <https://en.wikipedia.org/wiki/J002E3>

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bsenftner
intrusive advertising kills this post.

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ColinWright
Here's a link with fewer ads (I think - I have an ad blocker)

[http://www.airingnews.com/articles/130797/When-Part-of-
Apoll...](http://www.airingnews.com/articles/130797/When-Part-of-
Apollo-13-Reached-the-Moon)

