NASA Spacecraft To Fly By Mercury
1/14/2008, 2:05 a.m. EST
By ALEX DOMINGUEZ
The Associated Press
BALTIMORE (AP) — A NASA spacecraft will fly by the planet Mercury on Monday, the first visit to the sun's closest neighbor since the 1970s.
The space probe Messenger will skim 124 miles above the planet's surface, the first of three passes before it settles into orbit three years from now.
The flyby will provide up-close views and, in a few weeks, pictures.
"We're expecting some pretty major surprises out of this," said Faith Vilas, a Messenger scientist and director of the MMT Observatory at Mount Hopkins, Ariz.
Scientists are hoping that what they learn next week will help them begin to answer lingering questions about the planet's origin, magnetic field, atmosphere and what that means about our own planet.
Mercury is a "real oddball," said lead researcher Sean Solomon of the Carnegie Institution of Washington. The planet is so close to the sun that temperatures vary at the equator between day and night by 1,100 degrees. At the same time, there is also evidence of ice at the poles.
It's the smallest planet in the solar system. For comparison, if Earth were the size of a baseball, Mercury would be a golf ball.
"We really need better information on Mercury to make sure that our ideas on how the Earth and sister planets formed" are accurate, Solomon said.
Among the mysteries is Mercury's magnetic field, discovered by NASA's Mariner 10 in the 1970s.
Scientists had thought that because of its small size, the planet's core had long ago solidified and would not have a molten interior, the most common explanation for a magnetic field. Last year, scientists using powerful radar signals to examine Mercury's rotation found evidence of wobbling that they say shows the planet has a molten outer core. Messenger's magnetometer is expected to provide further clues.
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