MESSENGER, an acronym for MErcury Surface, Space ENvironment, GEochemistry and Ranging, is the first probe to visit Mercury since the three Mariner 10 flybys back in 1974/75.  As of the time of writing, this is where MESSENGER is located:

Where MESSENGER is located at 10:00 CDT, from the website

Launched August 3rd, 2004, MESSENGER hit the cosmos on a Delta II rocket, and is currently packing a Delta V rocket.  MESSENGER needs this extraordinarily powerful rocket to brake as it approached the Sun, and when it accomplishes orbit insertion because of the Sun’s gravity well.  MESSENGER will insert into a highly elliptical orbit because of the thrust required to slow it down.   MESSENGER will come as close as 125 miles (200 km) above the surface of Mercury on its orbit.

Just… WOW!

NASA image, building MESSENGER

In addition to its Mercury flybys, MESSENGER buzzed Earth and Venus.  It will begin braking for orbit insertion around March 18, 2011.  Lets keep our fingers crossed it doesn’t end up a little pile of rubble on Mercury’s surface, or get shot out of the solar system.  Of course, MESSENGER will eventually end as a pile of rubble on the surface of Mercury, but lets hope that doesn’t occur in 2011.

MESSENGER was designed to answer six questions:

• Why is Mercury so dense?
• What is the geologic history of Mercury?
• What is the nature of Mercury’s magnetic field?
• What is the structure of Mercury’s core?
• What are the unusual materials at Mercury’s poles?
• What volatiles are important at Mercury?

What we’ve learned so far is astonishing.  For instance, did you know there is water in Mercury’s exosphere?  Neither did the scientific community.  It wasn’t even suspected, but there it is.  Mercury also has volcanic activity, and a suspected liquid core.  Studies of Mercury will help us determine why the Earth is the way it is, and not like Venus or Mars.  Mercury is the “extremist” of the inner solar system.

MESSENGER on-board instruments, from the website

On MESSENGER’s third, and final, flyby, it entered “safe mode” for about 7 hours.  MESSENGER is designed to shut off communications with Earth if it senses something wrong.  It will go “safe”, and attempt to diagnose and repair itself.  When it re-established communication, everything tested fine.  We don’t know why it went into safe mode, but it did accomplish its gravity boost to shoot it around for orbit insertion.  For normal operations, MESSENGER is powered by its solar panels.

I recommend you take a moment to browse the MESSENGER website.  You’ll find mind-blowing images of Mercury, in addition to some great information.  There’s even a section for the kids.