Mercury is the innermost and smallest planet in the Solar System. Mercury is similar in appearance to the Moon: it is heavily cratered with regions of smooth plains, has no natural satellites and no substantial atmosphere. Surface temperatures range from about −183 °C to 427 °C, with the subsolar point being the hottest and the bottoms of craters near the poles being the coldest. (From Wikipedia)
Image is from the Mariner 10 spacecraft.
(Note the blank area in the upper right is from the lack of data in this region.)