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Intro music.

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When the Messenger spacecraft arrives on-orbit around Mercury in 2011, it will be the planet's first Earthly visitor in over 36 years.

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Our last trip to the planet was in 1975 with the flight of the Mariner 10 spacecraft.

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Launched in November of 1973, the craft completed a trio of flybys past Mercury.

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Across the span of its mission, Mariner 10 mapped about half of the planet's surface and even detected a faint atmosphere.

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With the flight Messenger, our curiosity once again turns to the peculiar features of Mercury.

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The planet's surface is a colorful patchwork of craters, plains and mile-high ridges.

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Below the surface rests a dense inner core that comprises an unusually high 42% of the planet's total volume.

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Mercury is also a planet of extremes.

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Mercury turns slowly on its own axis once every six months while it races around the Sun four times a year.

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Mercury also has an especially broad temperature range with highs of 801 degrees in the sun and -361 degrees on the planet's darkside.

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In 2011, the Messenger spacecraft will return to Mercury to pickup where Mariner 10 left off.

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And although 36 years will have passed since our last visit, the trip is sure to be worth the wait.

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