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Today, January 14, 2008, at 19:04:39 UTC (2:04:39 pm EST), MESSENGER will experience its closest approach to Mercury, passing just 200 kilometers (124 miles) above the planet's surface. As the MESSENGER spacecraft continues to speed toward Mercury, the Narrow Angle Camera, part of the Mercury Dual Imaging System (MDIS) instrument, acquired this crescent view of Mercury. The image was taken on January 13, 2008, when the spacecraft was at a distance of about 760,000 kilometers (470,000 miles) from Mercury. Mercury is about 4880 kilometers (about 3030 miles) in diameter, and this image has a resolution of about 20 kilometers/pixel (12 miles/pixel).

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Dwight, when was the last probe visit to Mercury? I cant think of anything since..what was it? the Mariner program?
 

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Good memory Vic. :) It was Mariner 10, the only probe ever to visit Mercury. It flew by Mercury twice in '74, once while inbound and again while outbound after looping around the sun. It only photographed 45% of Mercury's surface.

Mercury is mysterious in many ways. Where does its extremely tenuous atmosphere come from? Why does it have a magnetic field? It rotates very slowly (once every 59 days), and it's small enough that its core should have cooled down long ago, so what generates that field? Why does the planet contain so much iron?

These and other questions are ones NASA is hoping to shed some light on. :)
 

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And Messenger is an acronym. It's short for Mercury Surface, Space Environment, Geochemistry and Ranging with an added e.:D

Mark
 

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MESSENGER Flyby of Mercury
At 2:04 p.m. EST MESSENGER skimmed 200 kilometers (124 miles) above the surface of Mercury in the first of three flybys of the planet. Initial indications from the radio signals indicate the spacecraft is still operating nominally. The first science data return from the flyby was received today, just minutes before the closest approach point with the planet, as planned. 
“The engineers and operators at the Deep Space Network (DSN) in Goldstone, Calif., in conjunction with engineers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., pulled off a tremendous feat, acquiring and locking onto the downlink signal from the spacecraft within seconds, providing the necessary Doppler measurements for the Radio Science team” said MESSENGER Mission Systems Engineer Eric Finnegan, of APL.“ The spacecraft is continuing to collect imagery and other scientific measurements from the planet as we now depart Mercury from the illuminated side, documenting for the first time the previously unseen surface of the planet.”
Tomorrow at noon EST, the spacecraft will turn back towards the Earth to start down-linking the on-board stored data. Measurements of this Doppler signal from the spacecraft will allow improve knowledge of Mercury’s gravity field.

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Ultimately, Messenger will go into orbit around Mercury, so this isn't just a series of flybys. /DesktopModules/NTForums/themes/mls/emoticons/satisfied.gif
 
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