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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. Our last trip to the planet was in 1975 with the flight of the Mariner 10 spacecraft. Launched in November of 1973, the craft completed a trio of flybys past Mercury. Across the span of its mission, Mariner 10 mapped about half of the planet's surface and even detected a faint atmosphere. With the flight Messenger, our curiosity once again turns to the peculiar features of Mercury. The planet's surface is a colorful patchwork of craters, plains and mile-high ridges. Below the surface rests a dense inner core that comprises an unusually high 42% of the planet's total volume. Mercury is also a planet of extremes. Mercury turns slowly on its own axis once every six months while it races around the Sun four times a year. Mercury also has an especially broad temperature range with highs of 801 degrees in the sun and -361 degrees on the planet's darkside. In 2011, the Messenger spacecraft will return to Mercury to pickup where Mariner 10 left off. And although 36 years will have passed since our last visit, the trip is sure to be worth the wait.