The planet Mercury doesn't come up in many conversations. Even among people inclined to talk about astronomy and the solar system, Mercury isn't often at the center of discussion.
Jupiter? Sure. Saturn? Of course. But not Mercury.
However, that may change in the future as more about this small, dense, rocky planet just a skip and a throw from the Sun becomes known, thanks to the MESSENGER spacecraft, which has spent the past few months orbiting the planet.
On Thursday, NASA released several new images of the planet taken by MESSENGER -- Mercury Surface, Space Environment, Geochemistry, and Ranging -- and scientific discoveries from the spacecraft, the first to orbit the planet. Among the discoveries, researchers found the origin of energetic particles in the planet's magnetosphere and the nature of patchy, bright deposits on some crater floors (see Photo 6). Researchers have also found that though the planet looks awfully like our Moon, its composition and origins are quite different.
Altogether, NASA estimates that the MESSENGER program -- from initial designs to ongoing operations now that the craft is orbiting Mercury -- cost about $446 million. It's scheduled to orbit Mercury for one Earth year, which is equivalent to about four Mercury years or two Mercury days (yes, days are longer than years on Mercury).
Below are photos of Mercury from the MESSENGER spacecraft.