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Astronuc
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« Reply #30 on: August 03, 2004, 04:01:05 PM » |
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By MARCIA DUNN, AP Aerospace Writer
The journey will take 6 1/2 years, covering nearly 5 billion miles on a roundabout ramble through the inner solar system. The probe should reach Mercury by March 2011, then spend a year gathering data.
Scientists want to know how the planet turned out the way it did, and whether the perpetually dark craters at the poles hold ice. Anything scientists can learn about how Mercury formed will shed light on the origins of Venus, Earth and Mars, each one very different.
The Messenger mission is part of NASA's bargain-focused Discovery program — $427 million for the launch and all the scientific analysis years later in a mission devised by Johns Hopkins University.
Scientists have been yearning to study Mercury up close ever since Mariner 10 zoomed by three times in the mid-1970s. If all goes well, Messenger will be the first spacecraft to orbit that planet.
Because it can't carry enough fuel, Messenger cannot fly straight to Mercury. So it will fly once past Earth, twice past Venus and three times past Mercury for gravity assists — and make 15 loops around the sun — before slowing enough to slip into orbit around the small, hot planet.
The heat encountered once in orbit will be the equivalent of 11 suns beating down on Earth, about 700 degrees. But its instruments will operate at room temperature, protected by a custom-built ceramic-fabric sunshade just one-quarter of an inch thick. All Mariner 10 had was a quaintly old-fashioned umbrella.
AP photo (1), Reuters photo (2)
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