In yet another NASA first, the robotic Messenger probe beamed back pictures this week of parts of the planet Mercury that never have been seen by spacecraft before.
Soon after sweeping within 124 miles of the planet's surface on Monday, Messenger snapped this photo of half of a hemisphere that was missed by the only other spacecraft to visit Mercury -- Mariner 10, which made three flybys in 1974 and 1975.
Mariner 10 was launched in November 1973 aboard an Atlas-Centaur rocket at Launch Complex 36B at Cape Canaveral Air Force Station. It only was able to image 45 percent of the surface of Mercury during its encounters with the planet.
The new Messenger image was taken with the spacecraft's wide-angle camera 80 minutes after its closest approach to the planet. Messenger was about 17,000 miles from the planet at the time.
A heavily-cratered surface is evident, and on the upper right is the giant Caloris basin, which was formed by an asteroid or comet that crashed onto the planet's surface. The interior of the basin is much lighter than darker smooth plains that surround it -- an indication that its composition is different.
The Messenger spacecraft captured more than 1,200 images and other data during the flyby earlier this week. It was the first of three that will slow the craft enough for it to drop into orbit around Mercury in 2011.
NASA will unveil more Messenger photos an analyses of data beamed back from its science instruments during a news conference on Jan. 30.
Photo credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington. The three entities are partnered together for the $446 million mission, which was launched from Cape Canaveral in August 2004.
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