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Hi, I'm Alicia and this is NASA Now.
Today we are going to go deep beneath the lunar surface
to see what's at the core of the moon.
We'll talk with an expert who uses seismic activity
to understand the structure of the moon.
That's ahead, but first here's what's happening at NASA Now.
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NASA's twin GRAIL spacecraft have set out to orbit the moon
in order to gain greater knowledge
of its interior structure.
NAT: 3,2,1,0 and liftoff of the Delta II with GRAIL -
journey to the center of the moon.
GRAIL will serve as eyes on the moon
for the student-run MoonKAM program.
MoonKAM stands for Moon Knowledge Acquired
by Middle Schools and it is an educational outreach program
that will allow you to take photos of the lunar surface
of the moon using eight different cameras
on the GRAIL spacecraft.
Students will use the images to study lunar features
such as craters and highlands, while also learning
about future landing sites.
In order to get involved in MoonKam, all you have
to do is have an educator register you online
at moonkam.ucsd.edu.
The GRAIL MoonKAM mission will begin in 2012
when the GRAIL satellites are in orbit around the moon
and the mission will last approximately 80 days.
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Another one of NASA's projects studying the interior
of the moon focuses on analyzing moonquakes,
that is seismic activity that occurs on the moon.
Joining us is Dr. Renee Weber, lunar and planetary scientist
at Marshall Space Flight Center.
Hello Dr. Weber, are moonquakes the same as earthquakes?
Plate tectonics are what causes most seismic activity
on the Earth.
The difference between the Earth and the moon is
that the moon has no plate tectonics.
You could sort of think of it as a solid shell.
So the seismic events recorded on the moon are a bit different
from types that are recorded on the Earth.
On the Moon we have three main types of seismic activity.
We have impacts, which is usually meteorites
that are actually impacting the surface of the moon.
Another type is shallow moonquakes.
They're not associated with plate boundaries,
but on the moon we don't really know what causes these
and they are relatively rare.
The third type of event that's recorded
on the moon is called the deep moonquake,
and these are much more frequent but they are very small.
So the deep moonquakes actually are related to the tides.
If you think about the moon orbiting the Earth,
you have a gravitational interaction
between these two bodies,
that interaction is what causes tides in the Earth's ocean.
And so these things come in and they go out
and it has a periodicity to it.
The same thing is what causes these deep moonquakes
on the moon.
What do you use to study activity on the moon?
I look mostly at seismic data from the Apollo missions,
which is sort of unique because it was the only extraterrestrial
seismic data set that we have.
So part of the Apollo science package included seismometers,
which measure ground motion, and there were four
of these instruments that were deployed
between the years 1969 and 1972.
And they recorded data up until 1977
and that is the data set that I analyze.
What can this data tell you about the moon?
We know on Earth that we have a crust and a mantle and a core.
The same thing is actually true of the moon
where we have a crust, mantle and a core.
But up until recently, we only knew roughly what the size
of the core was, whether or not it was molten,
what the materials are that it's made of.
So basically there are two types of seismic energy.
If you think about dropping a pebble into a pond,
you watch the ripple spread out from the source.
Well, the same thing is basically true of a moonquake.
So if you think of the moonquake as being a point inside the moon
that rumbles, it's sending energy out in spheres
from the central point.
So, some of that energy travels directly from the moonquake
up to the seismometers that sit on the surface and likewise,
some of that energy travels down.
So what happens with that energy that travels
down is it reaches the core and that actually reflects off
of the core mantle boundary and travels back
to the seismic station.
And we can use some knowledge of the seismic structure
of the moon to figure out exactly where the depth is based
on the travel times of those waves to the seismic stations.
How will your research continue?
There are still a lot of questions that we need
to know regarding the seismic activity
on the far side of the moon.
So one thing that we can do is continue
to apply modern seismology processing techniques
to see if we can learn more.
Another thing that we can do is we can take what we've learned
and try to apply it to designing new seismometers,
which will hopefully fly to the moon
on future lunar seismic missions.
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Did you know that the distance between Earth
and the moon changes constantly?
That's because the moon does not orbit Earth in a perfect circle,
but instead travels in a slightly elliptical orbit.
The moon's distance from Earth varies as much 26,000 miles
and this contributes
to the stresses associated with moonquakes.
Now you know.
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An important part of lunar exploration is mapping
your destination.
Check out this cool activity.
You can use some of the exact same techniques
as NASA engineers with Vector Addition:
Math and Science @ Work - Lunar Surface Instrumentation.
You can find it on the NASA Explorer Schools'
Virtual Campus.
Well that's it for NASA Now, join us next time
when we go horizontal on the treadmill.
And be sure to check us out on Facebook.
See you then on NASA Now.
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NASA Now comes to you from the Virtual Campus
at NASA Explorer Schools.