April 30, 2009: A NASA spacecraft gliding over the surface of
Mercury has revealed that the planet's atmosphere,
magnetosphere, and its geological past display greater levels of
activity than scientists first suspected. The probe also
discovered a large impact basin named "Rembrandt" measuring
about 430 miles in diameter. These new findings and more are
reported in four papers published in the May 1 issue of Science
magazine. The data come from the Mercury Surface, Space
Environment, Geochemistry, and Ranging spacecraft--MESSENGER for
short. On Oct. 6, 2008, MESSENGER flew by Mercury for the second
time, capturing more than 1,200 high-resolution and color images
of the planet. Right: The Rembrandt impact basin discovered by
MESSENGER during its second flyby of Mercury in October 2008.
Credit: NASA/Johns Hopkins University Applied Physics
Laboratory/Smithsonian Institution/Carnegie Institution of
Washington. [more] "This second Mercury flyby provided a number
of new findings," said Sean Solomon, the probe's pr