What Makes a Planet?

The inner planets of our solar system are Earth, Mercury, Venus and Mars. They are made up of mostly rock, minerals and metals such as aluminum and magnesium. Though Pluto is no longer considered a true planet it also has this make-up. The other 4 planets are made up of mostly gasses such as helium and hydrogen. Jupiter, Saturn, Uranus and Neptune are therefore called gas giants.You can find more information here: