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. read more
The inner planets (in order of distance from the sun, closest to furthest) are Mercury, Venus, Earth and Mars. After an asteroid belt comes the outer planets, Jupiter, Saturn, Uranus and Neptune. The interesting thing is, in some other planetary systems discovered, the gas giants are actually quite close to the sun. read more