NASA's Messenger spacecraft reveals hidden side of Mercury

Second flyby offers scientists 1,200 images as well as topographical and magnetic data

The planet Mercury is a lot less mysterious today than ever before.

Scientists are studying more than 1,200 pictures of the planet's surface, along with topographical information and data about its atmosphere and magnetic fields -- all thanks to the Messenger spacecraft's second flyby earlier this month. On Oct. 6, Messenger raced past Mercury, and armed with an array of six analysis instruments, it flew just 125 miles above the planet's cratered surface.

And now, scientists are knee-deep in new data that has been coming in from the spacecraft, which is on a path to move into an orbit around Mercury by March 2011. Messenger's first flyby of the planet was in January.

The images from Messenger arrived shortly after a probe to Mars successfully discovered ice on that planet. Instruments on the Phoenix Mars Lander conducted several tests on soil dug up by a robotic arm and discovered what scientists had been hoping to find -- elements that could support life.

The first two flybys of Mercury provided scientists with the first images and measurements of that planet's western hemisphere.

"The region of Mercury's surface that we viewed at close range for the first time this month is bigger than the land area of South America," said Sean Solomon, principal investigator and director of the department of terrestrial magnetism at the Carnegie Institution of Washington, in a statement. "When combined with data from our first flyby and from Mariner 10, our latest coverage means that we have now seen about 95% of the planet."

The Mariner 10 spacecraft flew to Mercury in the mid-1970s. It was the only spacecraft to visit the planet before Messenger.

The first images from the most recent flyby arrived on Earth earlier this month.

NASA scientists and engineers have spent about 20 years developing new materials and technologies for the Messenger. Its 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 a nickel-hydrogen battery reportedly give the spacecraft the power it needs.

The messenger uses two computer chips -- a 25-MHz main processor and a 10-MHz backup processor.

The spacecraft, according to documents on NASA's Web site, 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-ft. boom, and it will scan the planet for areas of magnetized rocks. And a dual-imaging system has wide-angle and narrow-angle imagers that should be able to map the surface and give scientists a topographical view.

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. That 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.

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