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A 124-mile view of Mercury's mysteries

Monday's flyby, the first visit in 33 years, is expected to render new images and data that can shed light on the origins of the solar system.

By Peter N. SpottsStaff writer of The Christian Science Monitor / January 14, 2008

Orbit: NASA's Messenger will examine Mercury's surface and collect images of the planet never before seen. The process is depicted in this artist's rendering.

NASA/Johns Hopkins University/Carnegie institution

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Astronomers are braced for surprises as the National Aeronautics and Space Administration's Messenger spacecraft Monday becomes the first robotic explorer to visit the planet Mercury in 33 years.

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At 2:04 p.m. Eastern time, Messenger will flit past the planet 124 miles above its surface at a blink-and-you-miss-it speed of 141,000 miles an hour. It's the first of three Mercury flybys the craft will perform in preparation for orbiting the planet, beginning in March 2011.

During the pass, the craft's camera is set to grab more than 1,200 exquisitely detailed images of the surface, covering large swaths of the planet that no human has ever seen before. Other instruments will provide the first assay of minerals and chemical elements on the surface, as well as measure Mercury's gravity and magnetic fields.

It's all in service to the question: What does this oddball planet tell us about how the solar system, especially the rocky inner planets, evolved?

"Mercury has been the Cinderella of the solar system for a long time, caught in the shadow of stepsisters Venus and Mars," says Sean Solomon, who heads the Department of Terrestrial Magnetism at the Carnegie Institution of Washington and is the mission's lead investigator. Between NASA's Messenger mission and missions to Mercury that Europe and Japan are pursuing, "that's about to change."

Mercury's evolutionary story is key to understanding the inner moons and inner planets of the solar system, notes Daniel Baker, who heads the Laboratory for Atmospheric and Space Physics at the University of Colorado at Boulder and is a member of the Messenger science team. "These close neighbors of the Earth are really important for us to understand our own origins."

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