In the universe, an asteroid belt physically separates and distinguishes the inner planets from the outer planets. This asteroid belt appears just after Mars and right before Jupiter. Mars bears the distinction of farthest inner planet from the sun while Jupiter takes recognition as the closest outer planet.
In the solar system, the inner planets include Mercury, Venus, Earth and Mars. These planets, in that order, span the distance from closest to furthest from the sun. The four inner planets are classified as terrestrial planets, which means their surfaces were formed from solid substances. Although classified as terrestrial, Earth is the only inner planet capable of supporting vast amounts of life.
The other planets contain some hospitable features, such as water and ice, but lack the climactic conditions suitable for growth. The cores and surfaces of the inner planets were formed primarily from metals and elements. Heavy metals of iron and nickel form the many layers of most inner planets. In contrast to the inner planets, the outer planets contain warmer atmospheres as they were formed from gases and liquids. These planets feature rings and many moons. Like the inner planets, outer planets vary in size. Jupiter, also the closest to the sun, is the largest.