MESSENGER- Historic Mercury Photographs

Yesterday, March 29, a historic photo of mercury was taken by the Messenger spacecraft.The Messenger is the first orbiting satellite around Mercury. Its first photo of the terrain was recieved on earth March 29.  Previous photos of Mercury had been taken by the Mariner, though the Mariner program was just a flyby. Currently the spacecraft has sent back to earth over 300 photos, and is working on global mapping of the planet. According to wikipedia, "the mission is designed to clear up six key issues: Mercury’s high density, its geological history, the nature of its magnetic field, the structure of its core, whether it has ice at its poles, and where its tenuous atmosphere comes from."
More info:
NASA Messenger 
MESSENGER official site