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.
Cloud Altitudes in Jovian Planet Atmospheres. The atmospheres of Jupiter and Saturn are made almost entirely of hydrogen and helium, although there is some evidence they contain hydrogen compounds. Uranus and Neptune are made primarily of hydrogen compounds, with smaller traces of hydrogen, helium, metal and rock. The most common hydrogen compounds are methane (CH4), ammonia (NH3), and water (H2O). The farther away a planet is from the Sun, the cooler its atmosphere will be.