From the picture above, a composite of images from the only other mission to Mercury by Mariner 10 and by MESSENGER itself on flybys, we can see that there are large parts of the planet for which we have no data at all.
I expect good things to come from this mission, including a mapping of Mercury’s curiously strong magnetic field.
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
Scale: Mercury’s diameter is 4880 kilometers (3030 miles)
Of Interest: The graphic shown here outlines in yellow the planned footprint for the first image to be acquired from a spacecraft orbiting Mercury. The image will be obtained as MESSENGER is high above Mercury’s south pole and will include a portion of Mercury’s surface not previously seen by spacecraft.
This first planned image is scheduled to be taken on March 29, 2011, 7:40 UTC, or 3:40 am EDT. Over the subsequent six hours, MESSENGER will acquire 364 images in total before beginning to downlink the data to Earth.
This image will be acquired during the commissioning phase of the MESSENGER mission, during which the spacecraft and instrument performance will be verified through a series of specially designed checkout activities. During the commissioning phase, MDIS will acquire 1549 images. The year-long primary science phase of the mission will begin on April 4, and the orbital observation plan calls for MDIS to acquire more than 75,000 images in support of MESSENGER’s science goals.