Colonization of the inner Solar System ESA "Moon Village" concepts. Colonization of the inner Solar System Bodies in the inner Solar System have been considered for terraforming and space colonization. The main candidates for colonization in the inner Solar System are Mars and Venus. Other possible candidates for colonization include the Moon and even Mercury. The short distance between the Earth and the Moon makes it a natural expansion after Earth. A number of government space agencies have periodically floated lunar plans such as Russia (2014), China (2012) and the US have made plans in constructing the first lunar outpost. The European Space Agency (ESA) head
Geology of solar terrestrial planets Their size, radius, and density are all similar. Terrestrial planets have numerous similarities to plutoids (objects like Pluto), which also have a solid surface, but are primarily composed of icy materials. During the formation of the Solar System, there were probably many more (planetesimals), but they have all merged with or been destroyed by the four remaining worlds in the solar nebula. The terrestrial planets all have roughly the same structure: a central metallic core, mostly iron, with a surrounding silicate mantle. The Moon is similar, but lacks a substantial iron core. Three of the four solar terrestrial planets (Venus,