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 outer solar nebula temperatures were cool enough for the abundant gases to accumulate and be held by proto-planets. As a result the Jovian planets (Jupiter, Saturn, Uranus, and Neptune) are gas giants, made mostly from hydrogen, helium, and hydrogen compounds like methane (CH 4) and ammonia (NH 3). Segregation of the Earth's Layers and Atmosphere