Neptune is an ice giant planet, and its atmosphere is mostly composed of hydrogen and helium with a small amount of methane. The blue color of Neptune is due to the presence of methane in its atmosphere. The planet has no definite surface layer, and its gas transitions into a slushy ice and water layer. The water-ammonia ocean serves as the planets mantle, and contains more than ten times the mass of Earth. Temperatures inside the mantle range from 3,140 degrees Fahrenheit (1,727 degrees Celsius) to 8,540 F (4,727 F) . Neptune has a rocky core made up of iron and other metals, with a mass just greater than that of Earth. Temperatures in the core could reach 9,260 F (5,127 C) . The planets interior is primarily composed of ices and rock, and its atmosphere forms about 5 to 10% of its mass and extends perhaps 10 to 20% of the way towards the core. Increasing concentrations of methane, ammonia, and water are found in the lower regions of the atmosphere.