There are eight planets in the Solar system, and each one is very diffirent. Some planets, like jupiter Saturn are very large. others, like Mercury and Mars are smaller. Jupiter has moons that are larger than Mercury. The planets also have diffirent atmospheres. Uranus, jupiterand Sturn have atmospheres of hydrogen and helium. The atmosphere on Venus is made up of carbon dioxde. Earth has a nitrogen and oxygen atmosphere. Neptune's atmosphere is mostly hydrogen. The planets also have diffirent temperatures. Uranus is the coldest and Venus is the hottest