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The Core of the Moon: The Moon's Core is Much Like Earth's

written by: Nick Oza•edited by: RC Davison•updated: 5/18/2011

The Moon's core has remained a controversial subject, open for debate among scientists. Recently, new data has emerged suggesting that the core of the Moon may be very similar to that of the Earth's. Read on to learn more about the interior of Earth's only natural satellite.

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    Why Study the Moon?

    Surface of the Moon 

    Before we talk about the Moon's core, it is important for us to understand why we must study the Moon in the first place. The Moon is the fifth largest satellite in our Solar System and the only natural satellite of the Earth. There are many effects that the Moon has on the Earth, the most obvious of which is tidal changes due to the Moon's gravity causing high and low tides. Another effect of the Moon on the Earth, however, not as obvious, is that the Moon's gravity causes a drag on the spin of the Earth, which leads to the Earth slowing down. This is why we have a 24-hour-day on Earth, and in the distant future the Earth will have longer days as it slows down even further.

    Another important reason to study the Moon is for the purpose of future colonization by humans. This may seem a little far fetched, but many scientists are talking about a journey to the Moon as a vacationing spot for Earthlings. Plans to mine the Moon for important resources is also on the drawing boards of many. It seems only logical to study the Moon for these reasons and many others and gain a understanding of it's makeup and origins.

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    The Moon's Core

    Interior of the Moon 

    Scientists generally disagreed upon the radius and size of the Moon's core. Data that was obtained from indirect measurement of the Moon's properties allowed scientists to formulate a model of the interior of the Moon, but nothing concrete. Recent findings by the National Aeronautics and Space Administration (NASA) have uncovered new details about the Moon's core. Seismometers that were left on the Moon by Apollo astronauts, recorded the activity of the moon's interior until 1977.

    A careful analysis of the data shows that the Moon's interior is very much like the Earth's. The inner core is made up of iron and is completely solid with a radius of around 240 km. The outer core is fluid, much like the Earth's outer core, extending up to 330 km. The only difference is that the Moon has a partially molten boundary layer around the core which extends up to 480 km. The core of the Moon is thought to contain lighter elements such as sulfur and oxygen, which have been indicated in the Earth's core. Sulfur makes up nearly six percent of the lunar core.

    Temperature within the core is around 830 degrees Celsius (1,530 degrees Fahrenheit) reducing gradually towards the surface. Heat traveling from the interior of the Moon to the surface is nearly half of that of the Earth's. Radioactive isotopes within the Moon's interior are much higher than those within the Earth and are responsible for the thermal evolution that takes place within the lunar interior. Moonquakes, similar to earthquakes, have been measured to take place between the outer core and the lithosphere by the seismometers left behind by the Apollo astronauts. The Moon's core, it seems, is very much like the Earth's.

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    Future Missions to Study the Moon's Core

    A better understanGRAIL Spacecraft ding of the lunar interior requires further missions to the Moon. One such NASA mission set to launch in 2011 is the Gravity Recovery and Interior Laboratory (GRAIL). The objective is to gain a better understanding of the Moon's interior. Scientists will be able to better explain the makeup of the crust, mantle and the core, from the physical properties to the chemical composition of the interior. An indirect study of the thermal evolution of the Moon is also one of the mission objectives.

    The mission will be executed by sending twin satellites to map the gravity of the Moon. A technique known as gravitational field mapping will reveal in great detail the lunar interior. Not only will scientists learn about the core, but they will also get clues to the origins of the moon, as well as the Earth.

    Middle schools from around the country will participate in the mission by sending in requests for the cameras on board GRAIL to take images of the lunar surface. The pictures will then become available online and students will be able to refer to them as they study the topography of the Moon.

    GRAIL's mapping of the Moon will be a significant step forward in learning about its structure. The analysis of the data relating to the deep interior of the Moon will help researchers better understand the Moon's core and the Earth's interior, and it will also influence future explorations of the Earth's satellite. The mapping of the Moon's gravity by GRAIL will also allow mission planners to calculate more precise orbits for future missions. The mission will also focus on learning more about the far side of the Moon and its polar regions.

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    Image Credits: Wikimedia Commons/RuM/Leny222/GDK/Contributions