Flying within 228 kilometers of the surface of Mercury on Sept. 29, the Messenger spacecraft snapped portraits of a portion of the planet that had never before been imaged close up.
Messenger also examined in greater detail Mercury’s western hemisphere, which had been imaged during a previous passage in October 2008 (SN Online: 10/29/08).
The Sept. 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 Sept. 30 and more are expected over the next few days.
Images: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
On September 29, 2009, the MESSENGER spacecraft passed by Mercury for the third time, flying 141.7 miles above the planet’s rocky surface for a final gravity assist that will enable it to enter orbit about Mercury in 2011. During the encounter, the MESSENGER cameras imaged a portion of Mercury’s never-before-seen surface and the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) observed Mercury’s exospheric “tail” during approach. With more than 90 percent of the planet’s surface already imaged, MESSENGER’s science team had drafted an ambitious observation campaign designed to tease out additional details from features uncovered during the first two flybys. But an unexpected signal loss prior to closest approach hampered those plans. – messenger.jhuapl.edu