Today in the innermost region of our solar system, NASA’s
Messenger space probe will swoop past Mercury for the third and
final time. The maneuver will give scientists a close look at
the dense, iron-rich, oddball planet, and will also alter the
probe’s trajectory and prepare it to begin orbiting Mercury in
March 2011. As Messenger travels within 142 miles of Mercury at
12,000 miles per hour, the spacecraft’s camera will swivel to
stare at a succession of craters and other geological features….
One target will be an old 90-mile-wide crater. Another will be
young 13-mile crater and a splash of light-colored soil
surrounding it. A third crater of interest has materials of
unusual color perhaps produced by violent volcanic eruptions
[The New York Times]. When this third flyby is complete, 95
percent of the planet will have been mapped in high resolution.
Scientists will also take a moment to examine the stream of
charged atoms that start at the planet’s surface and extend
millions of miles into space in a comet-