File:Solar System1.jpg The solar system is a system of planets, asteroid belt, clouds of dust and the sun. The sun is located at the centre and only ultimate energy source of the solar system. There are eight planets and 3 dwarf planets. Planets revolve around the sun and are themselves revolved about by small bodies called as satellites(or moons). There is an asteroid belt between the Jupiter and Mars. The planets whose orbits precedes to that of the asteroid belt are called inner planets(also sometimes rocky planets). Planets after the asteroid belt are called as Outer planets(also sometimes gas giants).
Earth is the only planet that retains life and has water. The other planets are either composed of rocks or gases. Venus was once(millions of years ago) said to contain water in large amounts(more than earth) but due to its more closeneess to the sun, the planet could not retain water and ended up with acids and sulphur dipxide. Mars also contained water about two million years ago and there had been a fossil evidence of bacteria too but due to the small size of mars the atmosphere couldn't be retained and almost three-fourth atmosphere declined over years. The oxygen combined rapidly with iron to form dry iron oxide.