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
Solar System of this entire region is less than the distance between the orbits of Jupiter and Saturn. This region is also within the frost line, which is a little less than 5 AU (about 700 million km) from the Sun. The four terrestrial or inner planets have dense, rocky compositions, few or no moons, and no ring systems. They are composed largely of refractory minerals, such as the silicateswhich form their crusts and mantlesand metals, such as iron and nickel, which form their cores. Three of the four inner planets (Venus, Earth and Mars) have atmospheres substantial enough to generate weather;