Mercury, Venus, Earth, and Mars are known as the terrestrial planets. In comparison to the outer planets, they are small in size, made of denser materials, and lack a huge numbers of moons. Even though they share these common traits, they are still very different from each other.
Mercury is the closest planet to the sun, yet its surface is either extremely hot or extremely cold due to the slow rotation of the planet on it's axis and the lack of atmosphere. It is also unique in that it's core is about 75% of its diameter, possibly due to an impact by a large body that shaved off some of the outer layers. Mercury's cratered and rugged terrain leaves spots of permanent shadow near its poles. Scientists suspect that there might be frozen water
Mercury is the closest planet to the sun, yet its surface is either extremely hot or extremely cold due to the slow rotation of the planet on it's axis and the lack of atmosphere. It is also unique in that it's core is about 75% of its diameter, possibly due to an impact by a large body that shaved off some of the outer layers. Mercury's cratered and rugged terrain leaves spots of permanent shadow near its poles. Scientists suspect that there might be frozen water