NANTES, France—NASA's Messenger spacecraft has been orbiting Mercury for more than six months, but that's all in a day's work, Mercury time. The orbiter has just passed its first Mercury solar day—about 176 Earth days—on the job, mission scientists reported here Wednesday at a joint meeting of the American Astronomical Society Division for Planetary Sciences and the European Planetary Science Congress. That's a significant milestone for Messenger's imaging campaign, because the orbiter has now seen almost the entire planet under similar solar lighting conditions.

The maps above represent two preliminary results from the observing campaign—a black-and-white map at high resolution and a false-color map at lower resolution. The false-color map displays 1,000-nanometer (infrared) light as red, 750-nanometer light (just on the border of red and infrared) as green, and 430-nanometer light (bluish purple) as blue. The few gaps that remain will be filled in during the second half of Messenger's one-year—or, if you prefer, two-Mercury-day—mission, the researchers said.