NASA’s Messenger spacecraft successfully achieved orbit around Mercury at approximately 2am UT friday morning, making it the innermost moon in our Solar system

This marks the first time a spacecraft has accomplished this engineering and scientific milestone at our solar system's innermost planet.

Previous spacecrafts has observerde Mercury, but all just passing by and has so far only been able to map 80% of Mercury's surface Messenger willbe capable of completing the mapping but in much higher details and with more scientific instruments.

For the next several weeks, APL engineers will be focused on ensuring the spacecraft’s systems are all working well in Mercury’s harsh thermal environment. Starting on March 23, the instruments will be turned on and checked out, and on April 4 the mission's primary science phase will begin.

This image was obtained by Messenger during a flyby manouver in 2008. It gives a good idea of what to expect, when Messenger starts its science operation

See Messengers homepage and DLR's Messenger news