Mercury

Mercury is the smallest planet in the solar system . It is the closest planet to the sun. It makes one trip around the sun once every 87.969 days . Mercury is bright when it is visible from Earth , ranging from -2.0 to 5.5 in apparent magnitude. It cannot be easily seen as it usually too close to the sun. Because Mercury is normally lost in the glase of the sun (except during a solar ellipse),Mercury can only be seen in the morning or evening twilight. Compared to what is known about the other planets in the solar system ,little is known about Mercury. Mercury is one of four inner planets in the solar system , and has a rocky body like the Earth. It is the smallest planet in the solar system , with a radius of 2,439.7 km(1,516.0 mi) Mercury is even smaller than some of the largest Moons in the solar system , such as Ganymede and titan. However, it has a greater mass than the largest Moons in the solar system. Mercury is made of about 70% metallic and 30% silicate material. Mercury density is the second highest in the solar system at 5.427 g/cm3,only a little bit less than Earth.