Mercury (planet)
Mercury is one of four terrestrial planets in the Solar System, and is a rocky body like Earth. It is the smallest planet in the Solar System, with an equatorial radius of . Mercury is also smaller—albeit more massive—than the largest natural satellites in the Solar System, Ganymede and Titan. Mercury consists of approximately 70% metallic and 30% silicate material. Mercury's density is the second highest in the Solar System at 5.427 g/cm, only slightly less than Earth's density of 5.515 g/cm. If the effect of gravitational compression were to be factored out from both planets, the materials of which Mercury is made would be denser than those of Earth, with an uncompressed density of 5.3 g/cm versus Earth's 4.4 g/cm.
Planets in astrology
Ceres () is the smallest identified dwarf planet in the Solar System, but is significantly the largest object in the asteroid belt. It was discovered on 1 January 1801 by Giuseppe Piazzi, and is named after Ceres, the Roman goddess of growing plants, the harvest, and of motherly love. It was the first asteroid discovered, taking up about one-third of the entire mass of its asteroid belt. The classification of Ceres has changed more than once and has been the subject of some disagreement. Johann Elert Bode believed Ceres to be the "missing planet" he had proposed to exist between Mars and Jupiter, at a distance of 419 million km (2.8 AU) from the Sun. Ceres was assigned a planetary symbol, and remained listed as a planet in astronomy books and tables for about half a century. The 2006 debate surrounding Pluto and what constitutes a planet led to Ceres being considered for reclassification as a planet, but in the end Ceres and Pluto were classified as the first members of the new dwarf planet category.