Mercury

Mercury is the closest planet to the Sun and obviously, is the hottest. It does not have a ring and is fairly large compared to others.

Appearance
Mercury is a brown colored planet, as seen from the photo. It appears to be very hilly with some kind of flat plane running from the middle of the planet, up. (see photo)

Missions
So far, NASA has not really done anything here except what they do for all planets. They took it's photo and are studying the planet. However, they have not landed on it or taken any evidence from the planet itself. It is unknown if they will do anything in the future.