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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.
