NASA spacecraft set to shine hot spotlight on Mercury

NASA is gearing up for the historic Jan. 14 spacecraft flight past planet Mercury that will explore some of the last major never-seen-before terrain in the inner solar system.  

During this month's Mercury pass the NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft's cameras and other sophisticated, high-technology instruments will take unprecedented images and make the first up-close measurements of the planet since Mariner 10 passed by in 1975.  

MESSENGER, launched in 2004,  is the first NASA mission sent to orbit Mercury, the planet closest to the sun. But on Jan. 14 it will pass close by the planet  and use Mercury's gravity for a critical assist needed to keep the spacecraft on track for its ultimate orbit around the planet three years from now. Still, the spacecraft is also expected to throw back some never-before –seen images, NASA said.  The flyby also will gather essential data for planning the overall mission. After flybys of Earth, Venus, and Mercury, it will start a year-long orbital study of Mercury in March 2011, NASA said. 

Specifically MESSENGER has two cameras -- one wide-angle, and one narrow-angle -- to help the "two-eyed" Mercury Dual Imaging System (MDIS) create a map of the planet's landforms, NASA said.   It will also trace different features on the surface. A special pivoting platform allows scientists to point the MDIS in whatever direction they choose.

The Mercury Laser Altimeter (MLA) will create topographic maps of the planet's surface in unprecedented detail. When the laser shines down and reflects off Mercury's surface, a sensor will gather the light, allowing scientists to track variations in the distance from the surface to the spacecraft. Once MESSENGER does orbit Mercury's surface, the spacecraft will be attracted to areas where the mass is greater and gravity tugs a little harder, causing it to speed up slightly as it approaches and slow a bit as it recedes.

A Radio Science experiment will use the Doppler Effect to track the changes in MESSENGER's velocity, and translate them into clues to how the planet's mass is distributed and where the crust is thicker or thinner, NASA said. 

Three instruments will rely on a process called spectroscopy to tell scientists what elements are present in the rocks and minerals around the planet. The X-ray Spectrometer (XRS) will detect X-rays emitted by certain elements in Mercury's crust. The Gamma Ray and Neutron Spectrometer (GRNS) works in much the same way, detecting gamma rays and neutrons emitted by various elements. GRNS may also help to determine if water ice really exists in permanently-shadowed craters at the planet's north and south poles -- as previous observations suggest. The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) will be able to determine Mecury’s atmosphere and also detect minerals on the surface. The instrument is extremely sensitive to light from the infrared to the ultraviolet, NASA said. 

Until now, NASA’s Mariner 10 was the first and only spacecraft to reach Mercury, according to NASA’s Web site.  Mariner 10 flew to within 460 miles of Mercury on March 29, 1974. It swept past the planet again on Sept. 24, 1974, and on March 16, 1975. During those flights, the spacecraft photographed portions of the surface of Mercury. It also detected Mercury's magnetic field, according to NASA’s Web site.

Some Mercury facts from NASA:  

·          Mercury is the planet nearest the sun. It has a diameter of 3,032 miles, about two-fifths of Earth's diameter. Mercury orbits the sun at an average distance of about 36 million miles (58 million kilometers), compared with about 93 million miles for Earth.  

·          Because of Mercury's size and nearness to the brightly shining sun, the planet is often hard to see from the Earth without a telescope. At certain times of the year, Mercury can be seen low in the western sky just after sunset. At other times, it can be seen low in the eastern sky just before sunrise.  

·          Mercury travels around the sun in an elliptical (oval-shaped) orbit. The planet is about 28,580,000 miles from the sun at its closest point, and about 43,380,000 miles from the sun at its farthest point. Mercury is about 48,000,000 miles from Earth at its closest approach.  

·          Mercury moves around the sun faster than any other planet. The ancient Romans named it Mercury in honor of the swift messenger of their gods. Mercury travels about 30 miles per second, and goes around the sun once every 88 Earth days. The Earth goes around the sun once every 365 days, or one year.  

·          As Mercury moves around the sun, it rotates on its axis, an imaginary line that runs through its center. The planet rotates once about every 59 Earth days -- a rotation slower than that of any other planet except Venus. As a result of the planet's slow rotation on its axis and rapid movement around the sun, a day on Mercury -- that is, the interval between one sunrise and the next -- lasts 176 Earth days.  

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