This image of Mercury, acquired by the Mercury Dual Imaging System (MDIS) aboard NASA's MESSENGER mission on April 23, 2013, allows us to take a step back to view the planet. Prior to the MESSENGER mission, Mercury's surface was often compared to the surface of Earth's moon, when in fact, Mercury and the moon are very different. This image in particular highlights many basins near Mercury's terminator, including Bach crater. Many craters with central peaks and the nearby bright rays of Han Kan crater are also evident.
Once per week, MDIS captures images of Mercury's limb, with an emphasis on imaging the southern hemisphere limb. These limb images provide information about Mercury's shape and complement measurements of topography made by the Mercury Laser Altimeter (MLA) of Mercury's northern hemisphere.