By Ron Cowen
Flying within 228 kilometers of the surface of Mercury on September 29, the MESSENGER spacecraft snapped portraits of a portion of the planet that had never before been imaged close-up.
The September 29 encounter was the third and last flyby and gave the craft the gravitational assistance it needs to settle in March 2011 into a yearlong orbit around Mercury, the solar system’s innermost and least explored planet.
The first images from the latest encounter, which detail 5 percent of the planet that hadn’t been examined by spacecraft before, were released on September 30 and more are expected over the next few days.