Terrestrial Planetsare those that have solid surfaces. They are all differentiated. Each has some amount of iron in its core. They may or may not have a thin atmosphere, usually consisting of carbon dioxide. Only Earth has an appreciable magnetic field. Earth also rotates the fastest of all the terrestrials. The terrestrial planets include Mercury, Venus Earth and Mars. I include the Moon in this group since it is very nearly the size of Mercury. Earth’s solitary moon could very easily be recognized as a planet if it orbited the Sun rather than the Earth. Below you see these five bodies to the correct relative scale. Click on each image for more detail.