Mercury is the closest planet to the sun. Because of this, Mercury is often hard to see from the earth. However, pictures from a spacecraft have shown that this planet is covered with craters, or bowl-shaped holes. Such craters are often made by large rocks which fall from the sky.
            It has also been learned that Mercury has some of the same gases that are found in the air on the earth.
            Mercury has no moon. Scientists believe that the sunny side of Mercury is about seven times the temperature of the hottest day on earth.
            Period of revolution: 88 days. Period of rotation: 59 days. Main components of atmosphere: none. Known moons: 0. Temperatures: Day 329°C; Night 27°C(?).