Mercury is the smallest planet in the solar system and also the closest to the Sun. Its orbit around the Sun takes only about 88 days, which is the shortest of all planets in the solar system. Its surface has many craters, much like the Moon, and it has almost no atmosphere to retain heat. Temperatures on Mercury can range from −173 °C all the way to 427 °C. The planet is named after the Roman god of the same name, who was the god of shopkeepers, merchants, travelers, and tricksters.