History of Solar System formation and evolution hypotheses equals c. 2000 trillion trillion kg; Earth is at about 6 trillion trillion kg). T Tauri (see T Tauri type stars) eruptions of the Sun stripped the gases away from the inner planets. Mercury was incompletely condensed and a portion of its gases were stripped away and transported to the region between Mars and Jupiter, where it fused with in-falling oxidized condensate from the outer reaches of the Solar System and formed the parent material for ordinary chondrite meteorites, the Main-Belt asteroids, and veneer for the inner planets, especially Mars. The differences between the inner planets are primarily the consequence
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,