04.30.09
Analyses of data from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft’s second flyby of Mercury in October 2008 show that the planet’s atmosphere, magnetosphere, and geological past are all characterized by much greater levels of activity than scientists first suspected.
On October 6, 2008, the probe flew by Mercury for the second time, capturing more than 1,200 high-resolution and color images of the planet, unveiling another 30 percent of Mercury’s surface that had never before been seen by spacecraft, and gathering essential data for planning the remainder of the mission.
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The remarkably well preserved Rembrandt impact basin was discovered by MESSENGER during its second flyby of Mercury. Most large impact basins on Mercury, the Moon, and other inner planets are flooded by volcanic flows that cover their entire floor. The number per area and size distribution of impact craters superposed on Rembrandt’s rim indicates that it is one of the youngest impact basins on Mercury. With a diameter of more than 430 miles, this feature on Earth would encompass the cities of Washington, D.C., and Boston, Massachusetts, and everything in between.
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Smithsonian Institution/Carnegie Institution of Washington |
“MESSENGER’s second Mercury flyby provided a number of new findings,” says MESSENGER Principal Investigator Sean Solomon at the Carnegie Institution of Washington. “One of the biggest surprises was how strongly the planet’s magnetospheric dynamics changed from what we saw during the first Mercury flyby in January 2008. Another was the discovery of a large and unusually well preserved impact basin that was the focus for concentrated volcanic and deformational activity. The first detection of magnesium in Mercury’s exosphere and neutral tail provides confirmation that magnesium is an important constituent of Mercury’s surface materials. And our nearly global imaging coverage of the surface after this flyby has given us fresh insight into how the planet's crust was formed.”
These findings are reported in four papers published in the May 1 issue of Science magazine.
For summaries of the findings reported in Science, click here.
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