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At approximately 9 p.m. EDT Thursday, NASA's MESSENGER (MErcury Surface, Space ENvironment, GEochemistry and Ranging orbiter) went into orbit around Mercury. "This marks the first time a spacecraft has accomplished this engineering and scientific milestone at our solar system's innermost planet," NASA announced.

Launched back in August of 2004 to study the geology, chemical composition and magnetic field of the planet, MESSENGER carries several advanced scientific instruments, including a neutron spectrometer and magnetometer. "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," NASA explained. "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."

The image above is an artist's concept of MESSENGER in orbit around Mercury.

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Image: NASA.

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