Big Jovian Worlds. They have no solid surfaces. They are less dense with thicker atmospheres and much smaller cores. All of them contain a ring, but Saturn's is the most prominent. There are two types of giant planets: ice giants and gas giants. Jupiter and Saturn are gas giants. This means their composition is mostly hydrogen and helium. Additionally, their cores are composed of liquid metallic hydrogen unlike iron and nickel seen inside terrestrial planets. Uranus and Neptune are ice giants meaning their compositions are mostly elements heavier than hydrogen and helium. This includes oxygen, nitrogen, carbon, and sulfur. Since Uranus and Neptune are much smaller compared to Jupiter and Saturn, their cores aren't liquid metallic hydrogen. Instead, it is a little rocky and icy. From the closest to the farthest: Jupiter, Saturn, Uranus, and Neptune.