The National Aeronautics and Space Administration's Mercury Surface, Space Environment, Geochemistry and Ranging spacecraft, known as Messenger, has measured the planet's atmosphere, the interaction of its surrounding magnetic field with the solar wind, and its geological past. The probe also discovered a previously unknown impact basin about 430 miles in diameter.
On Oct. 6 the probe flew by Mercury for the second time, capturing more than 1,200 high-resolution and color images of the planet. Messenger unveiled another 30 percent of the planet's surface that hadn't been seen by previous spacecraft, gathering essential data for planning the remainder of the mission.
"This second Mercury flyby provided a number of new findings," said Sean Solomon, Messenger's principal investigator from the Carnegie Institution of Washington. "One of the biggest surprises was how strongly the dynamics of the planet's magnetic field changed from what we saw during the first Mercury flyby in January 2008. The discovery of a large and unusually well preserved impact basin shows concentrated volcanic and deformational activity."
The new findings are reported in four papers published in the May 1 issue of Science magazine.