Gas giants are a class of planets that are very different from the rocky planets such as Earth. Composed primarily of hydrogen and helium, gas giants have no defined solid surface, and instead possess thick atmospheres of gas and liquid. This gas and liquid are constantly in motion due to convection currents caused by the intense heat and gravity of the planet’s core. Gas giants have a variety of unique features, such as thick cloud layers, strong winds, and powerful magnetic fields that extend far beyond the planet’s surface.