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NASA spacecraft closes in on Mercury, looking for ice

Armed with an array of six instruments for analysis, NASA's Messenger spacecraft is closing in on Mercury where it will take more than 1,200 pictures and hopefully help scientists figure out whether there is ice on the planet closest to the sun.

NASA estimates that Messenger, which made its first pass of Mercury in January, will make the second of three passes on Monday, Oct. 6.

The effort will come just weeks after the Mars Lander used its robotic arm and several onboard instruments to discover the presence of ice on the Red Planet. Using an orbiter, two Rovers and the Lander, scientists are working to figure out if Mars holds the elements that support life -- and possibly even discover if some form of life ever existed there.

Taking pictures of Mercury's as-of-yet-unseen surface, the Messenger spacecraft will fly by 125 miles above the planet, assessing its gravity and atmosphere to help scientists move Messenger into orbit around Mercury in March of 2011.

If all goes as planned, Messenger will be the first spacecraft to orbit the planet, which is only 58 million kilometers from the sun. In comparison, the Earth is 149,600,000 kilometers from the sun

"The results from Messenger's first flyby of Mercury resolved debates that are more than 30 years old," said Sean Solomon, the mission's principal investigator from the Carnegie Institution of Washington, in a statement. "This second encounter will uncover even more information about the planet."

According to NASA, only one spacecraft before Messenger visited Mercury -- Mariner 10 in 1974 and 1975. That early spacecraft was programmed to fly by the planet three different times to take photos of its cratered surface. The problem was that the probe took pictures of the same side of Mercury on each flyby.

Messenger is being programmed to get images of different areas of the planet, including its northern pole, where some scientists surmise there might be ice.

And finding ice would be a major discovery on a planet that is so close to the sun that its surface is 11 times brighter than Earth's. NASA noted in online documents that while Mercury's surface temperatures can reach about 840 degrees Fahrenheit, deep craters near its poles are in shade and there the temperature can plummet to minus 350 degrees Fahrenheit.

NASA scientists and engineers have spent about 20 years developing new materials and technologies for the Messenger. Its very structure was built out of a graphite epoxy material that was designed to be strong enough to withstand the launch yet light enough to lower the probe's overall mass and save on energy usage. Two large solar panels and nickel-hydrogen battery reportedly give the spacecraft the power it needs.

For computer chips, Messenger users two - a 25MHz main processor and a 10MHz backup processor.

The spacecraft, according to documents on NASA's website, include a gamma-ray and neutron spectrometer that is designed to map different elements and offer clues about the existence of ice at the planet's poles. A magnetometer is attached to a nearly 12-foot boom and it will scan the planet for areas of magnetized rocks. And a dual imaging system has a wide-angle and narrow-angle imagers that should be able to map the surface and give scientists a topographical view.

"We will be able to do the first test of differences in the chemical compositions between the two hemispheres viewed in the two flybys," said Ralph McNutt, the mission's project scientist, in a written statement. "Instruments also will provide information about portions of Mercury's surface in unprecedented detail."