Messenger, which stands for MErcury Surface, Space ENvironment, GEochemistry, and Ranging mission, is the first orbital mission to travel around the closest planet to the Sun, according to SPACE.com.
The 1,000-pound spacecraft left for Mercury on Aug. 3, 2004 and has been sending back pictures and information about the planet's craters and how its mysterious landscape was formed.
The spacecraft's trip to the Sun's closest planetary neighbor used the gravity of Earth, Venus and Mercury to slingshot it from place to place using the least amount of fuel possible.
Messenger did several flybys of Mercury through which it revealed many previously unknown features of the planet, but scientists are most excited about mapping the planet's unseen side.
"We can now say we have imaged every square meter of Mercury's surface from orbit," said Messenger principal investigator Sean Solomon of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.
"Admittedly, some regions are in permanent shadow, but we're actually peering into those shadows with our imaging systems."
Before Messenger, NASA had mapped less than half the surface of Mercury through the Mariner 10 spacecraft, which made several flybys of Mercury in 1974 and 1975.
"When we set out with the Messenger mission we didn't know if the planet would look like the other half that was seen in the '70s," Solomon told SPACE.com. "There was a great debate over how important volcanism was in the history of Mercury."
According to Yahoo News, Messenger confirmed that volcanism did occur in Mercury in the past and that it was a widespread phenomenon. In addition, the spacecraft shed exposed never-before-seen types of terrain on the planet including pockmarked surfaces called hollows which "scientists suspect are created when volatile materials sublimate off the surface."
Messenger's primary mission originally ran though March 2012, but was granted a one-year extension unti March 2013.
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