Cell division is the process by which a parent cell divides into two or more daughter cells. Cell division usually occurs as part of a larger cell cycle.
Neptune's atmosphere, like Jupiter's and Saturn's, is composed primarily of hydrogen and helium, along with traces of hydrocarbons and possibly nitrogen; it contains a higher proportion of ices such as water, ammonia, and methane.
In the top one-fourth of the planet, the pressure and temperature are so high that the hydrogen atoms are stripped of their outer electrons, forming a liquid metal. Like Jupiter, Saturn has a thick atmosphere composed of hydrogen and helium. The ratio of hydrogen to helium ratio decreases with depth. Methane and ammonia are also present. The atmosphere of Saturn envelops a thick layer of metallic hydrogen. The atmosphere of Neptune consists mainly of hydrogen and helium, but about 2.5-3% of the atmosphere is methane. Like Uranus, clouds in Neptune's atmosphere are composed of crystals of methane. -=-=-=-=- Since gas giants do not actually have a surface, it is rather difficult to determine where their atmospheres end.